建筑给排水_外文文献翻译1
给水排水工程专业外文翻译--密封的建筑排水系统和通气系统
外文原文：Sealed building drainage and vent systems—an application of active air pressure transient control and suppression AbstractThe introduction of sealed building drainage and vent systems is considered a viable proposition for complex buildings due to the use of active pressure transient control and suppression in the form of air admittance valves and positive air pressure attenuators coupled with the interconnection of the network's vertical stacks.This paper presents a simulation based on a four-stack network that illustrates flow mechanisms within the pipework following both appliance discharge generated, and sewer imposed, transients. This simulation identifies the role of the active air pressure control devices in maintaining system pressures at levels that do not deplete trap seals.Further simulation exercises would be necessary to provide proof of concept, and it would be advantageous to parallel these with laboratory, and possibly site, trials for validation purposes. Despite this caution the initial results are highly encouraging and are sufficient to confirm the potential to provide definite benefits in terms of enhanced system security as well as increased reliability and reduced installation and material costs.Keywords: Active control; Trap retention; Transient propagationNomenclatureC+-——characteristic equationsc——wave speed, m/sD——branch or stack diameter, mf——friction factor, UK definition via Darcy Δh=4fLu2/2Dgg——acceleration due to gravity, m/s2K——loss coefficientL——pipe length, mp——air pressure, N/m2t——time, su——mean air velocity, m/sx——distance, mγ——ratio specific heatsΔh——head loss, mΔp——pressure difference, N/m2Δt——time step, sΔx——internodal length, mρ——density, kg/m3Article OutlineNomenclature1. Introduction—air pressure transient control and suppression2. Mathematical basis for the simulation of transient propagation in multi-stack building drainage networks3. Role of diversity in system operation4. Simulation of the operation of a multi-stack sealed building drainage and vent system5. Simulation sign conventions6. Water discharge to the network7. Surcharge at base of stack 18. Sewer imposed transients9. Trap seal oscillation and retention10. Conclusion—viability of a sealed building drainage and vent system1.Air pressure transients generated within building drainage and vent systems as a natural consequence of system operation may be responsible for trap seal depletion and cross contamination of habitable space [1]. Traditional modes of trap seal protection, based on the Victorian engineer's obsession with odour exclusion [2], [3] and [4], depend predominantly on passive solutions where reliance is placed on cross connections and vertical stacks vented to atmosphere [5] and [6]. This approach, while both proven and traditional, has inherent weaknesses, including the remoteness of the vent terminations [7], leading to delays in the arrival of relieving reflections, and the multiplicity of open roof level stack terminations inherent within complex buildings. The complexity of the vent system required also has significant cost and space implications [8].The development of air admittance valves (AAVs) over the past two decades provides the designer with a means of alleviating negative transients generated as random appliance discharges contribute to the time dependent water-flow conditions within the system. AAVs represent an active control solution as they respond directly to the local pressure conditions, opening as pressurefalls to allow a relief air inflow and hence limit the pressure excursions experienced by the appliance trap seal [9].However, AAVs do not address the problems of positive air pressure transient propagation within building drainage and vent systems as a result of intermittent closure of the free airpath through the network or the arrival of positive transients generated remotely within the sewer system, possibly by some surcharge event downstream—including heavy rainfall in combined sewer applications.The development of variable volume containment attenuators [10] that are designed to absorb airflow driven by positive air pressure transients completes the necessary device provision to allow active air pressure transient control and suppression to be introduced into the design of building drainage and vent systems, for both ‘standard’ buildings and those requiring particular attention to be paid to the security implications of multiple roof level open stack terminations. The positive air pressure attenuator (PAPA) consists of a variable volume bag that expands under the influence of a positive transient and therefore allows system airflows to attenuate gradually, therefore reducing the level of positive transients generated. Together with the use of AAVs the introduction of the PAPA device allows consideration of a fully sealed building drainage and vent system.Fig. 1 illustrates both AA V and PAPA devices, note that the waterless sheath trap acts as an AA V under negative line pressure.Fig. 1. Active air pressure transient suppression devices to control both positive and negative surges.Active air pressure transient suppression and control therefore allows for localized intervention to protect trap seals from both positive and negative pressure excursions. This hasdistinct advantages over the traditional passive approach. The time delay inherent in awaiting the return of a relieving reflection from a vent open to atmosphere is removed and the effect of the transient on all the other system traps passed during its propagation is avoided.2.Mathematical basis for the simulation of transient propagation in multi-stack building drainage networks.The propagation of air pressure transients within building drainage and vent systems belongs to a well understood family of unsteady flow conditions defined by the St Venant equations of continuity and momentum, and solvable via a finite difference scheme utilizing the method of characteristics technique. Air pressure transient generation and propagation within the system as a result of air entrainment by the falling annular water in the system vertical stacks and the reflection and transmission of these transients at the system boundaries, including open terminations, connections to the sewer, appliance trap seals and both AAV and PAPA active control devices, may be simulated with proven accuracy. The simulation [11] provides local air pressure, velocity and wave speed information throughout a network at time and distance intervals as short as 0.001 s and 300 mm. In addition, the simulation replicates local appliance trap seal oscillations and the operation of active control devices, thereby yielding data on network airflows and identifying system failures and consequences. While the simulation has been extensively validated [10], its use to independently confirm the mechanism of SARS virus spread within the Amoy Gardens outbreak in 2003 has provided further confidence in its predictions [12].Air pressure transient propagation depends upon the rate of change of the system conditions. Increasing annular downflow generates an enhanced entrained airflow and lowers the system pressure. Retarding the entrained airflow generates positive transients. External events may also propagate both positive and negative transients into the network.The annular water flow in the ‘wet’ stack entrains an airflow due to the condition of ‘no slip’ established between the annular water and air core surfaces and generates the expected pressure variation down a vertical stack. Pressure falls from atmospheric above the stack entry due to friction and the effects of drawing air through the water curtains formed at discharging branch junctions. In the lower wet stack the pressure recovers to above atmospheric due to the traction forces exerted on the airflow prior to falling across the water curtain at the stack base.The application of the method of characteristics to the modelling of unsteady flows was first recognized in the 1960s [13]. The relationships defined by Jack [14] allows the simulation to model the traction force exerted on the entrained air. Extensive experimental data allowed the definition of a ‘pseudo-friction factor’ applicable in the wet stack and operable across the water annular flow/entrained air core interface to allow combined discharge flows and their effect on airentrainment to be modelled.The propagation of air pressure transients in building drainage and vent systems is defined by the St Venant equations of continuity and momentum [9],(1)(2)These quasi-linear hyperbolic partial differential equations are amenable to finite difference solution once transformed via the Method of Characteristics into finite difference relationships, Eqs. (3)–(6), that link conditions at a node one time step in the future to current conditions at adjacent upstream and downstream nodes, Fig. 2.Fig.2. St Venant equations of continuity and momentum allow airflow velocity and wave speed to bepredicted on an x-t grid as shown. Note , .For the C+ characteristic:(3)when(4)and the C- characteristic:(5)when(6)where the wave speed c is given byc=(γp/ρ)0.5. (7) These equations involve the air mean flow velocity, u, and the local wave speed, c, due to the interdependence of air pressure and density. Local pressure is calculated as(8)Suitable equations link local pressure to airflow or to the interface oscillation of trap seals.The case of the appliance trap seal is of particular importance. The trap seal water column oscillates under the action of the applied pressure differential between the transients in the network and the room air pressure. The equation of motion for the U-bend trap seal water column may be written at any time as(9)It should be recognized that while the water column may rise on the appliance side, conversely on the system side it can never exceed a datum level drawn at the branch connection.In practical terms trap seals are set at 75 or 50 mm in the UK and other international standards dependent upon appliance type. Trap seal retention is therefore defined as a depth less than the initial value. Many standards, recognizing the transient nature of trap seal depletion and the opportunity that exists for re-charge on appliance discharge allow 25% depletion.The boundary equation may also be determined by local conditions: the AAV opening and subsequent loss coefficient depends on the local line pressure prediction.Empirical data identifies the AAV opening pressure, its loss coefficient during opening and at the fully open condition. Appliance trap seal oscillation is treated as a boundary condition dependent on local pressure. Deflection of the trap seal to allow an airpath to,or from, the appliance or displacement leading to oscillation alone may both be modelled. Reductions in trap seal water mass during the transient interaction must also be included.3. Role of diversity in system operationIn complex building drainage networks the operation of the system appliances to discharge water to the network, and hence provide the conditions necessary for air entrainment and pressure transient propagation, is entirely random. No two systems will be identical in terms of their usage at any time. This diversity of operation implies that inter-stack venting paths will be established if the individual stacks within a complex building network are themselves interconnected. It is proposed that this diversity is utilized to provide venting and to allow serious consideration to be given to sealed drainage systems.In order to fully implement a sealed building drainage and vent system it would be necessary for the negative transients to be alleviated by drawing air into the network from a secure space andnot from the external atmosphere. This may be achieved by the use of air admittance valves or at a predetermined location within the building, for example an accessible loft space.Similarly, it would be necessary to attenuate positive air pressure transients by means of PAPA devices. Initially it might be considered that this would be problematic as positive pressure could build within the PAPA installations and therefore negate their ability to absorb transient airflows. This may again be avoided by linking the vertical stacks in a complex building and utilizing the diversity of use inherent in building drainage systems as this will ensure that PAPA pressures are themselves alleviated by allowing trapped air to vent through the interconnected stacks to the sewer network.Diversity also protects the proposed sealed system from sewer driven overpressure and positive transients. A complex building will be interconnected to the main sewer network via a number of connecting smaller bore drains. Adverse pressure conditions will be distributed and the network interconnection will continue to provide venting routes.These concepts will be demonstrated by a multi-stack network.4. Simulation of the operation of a multi-stack sealed building drainage and vent systemFig. 3 illustrates a four-stack network. The four stacks are linked at high level by a manifold leading to a PAPA and AAV installation. Water downflows in any stack generate negative transients that deflate the PAPA and open the AAV to provide an airflow into the network and out to the sewer system. Positive pressure generated by either stack surcharge or sewer transients are attenuated by the PAPA and by the diversity of use that allows one stack-to-sewer route to act as a relief route for the other stacks.The network illustrated has an overall height of 12m. Pressure transients generated within thenetwork will propagate at the acoustic velocity in air . This implies pipe periods, from stack base to PAPA of approximately 0.08s and from stack base to stack base of approximately 0.15s.In order to simplify the output from the simulation no local trap seal protection is included—for example the traps could be fitted with either or both an AAV and PAPA as examples of active control. Traditional networks would of course include passive venting where separate vent stacks would be provided to atmosphere, however a sealed building would dispense with this venting arrangement.Fig.3.Four stack building drainage and vent system to demonstrate the viability of a sealed building system.Ideally the four sewer connections shown should be to separate collection drains so that diversity in the sewer network also acts to aid system self venting. In a complex building this requirement would not be arduous and would in all probability be the norm. It is envisagedthat the stack connections to the sewer network would be distributed and would be to a below ground drainage network that increased in diameter downstream. Other connections to the network would in all probability be from buildings that included the more traditional open vent system design so that a further level of diversity is added to offset any downstream sewer surcharge events of long duration. Similar considerations led to the current design guidance for dwellings.It is stressed that the network illustrated is representative of complex building drainage networks. The simulation will allow a range of appliance discharge and sewer imposed transient conditions to be investigated.The following appliance discharges and imposed sewer transients are considered:1. w.c. discharge to stacks 1–3 over a period 1–6s and a separate w.c. discharge to stack 4 between 2 and 7s.2. A minimum water flow in each stack continues throughout the simulation, set at 0.1L/s, to represent trailing water following earlier multiple appliance discharges.3. A 1s duration stack base surcharge event is assumed to occur in stack 1 at 2.5s.4. Sequential sewer transients imposed at the base of each stack in turn for 1.5s from 12 to 18s.The simulation will demonstrate the efficacy of both the concept of active surge control and inter-stack venting in enabling the system to be sealed, i.e. to have no high level roof penetrations and no vent stacks open to atmosphere outside the building envelope.The imposed water flows within the network are based on ‘real’ system values, being representative of current w.c. discharge characteristics in terms of peak flow, 2l/s, overall volume, 6l, and duration, 6s. The sewer transients at 30mm water gauge are representative but not excessive. Table 1 defines the w.c. discharge and sewer pressure profiles assumed.Table1. w.c. discharge and imposed sewer pressure characteristicsw.c. discharge characteristic Imposed sewer transient at stack baseTime Discharge flow Time PressureSeconds l/s Seconds Water gauge (mm)Start time 0.0 Start time 0.0+2 2.0 +0.5 30.0+4 2.0 +0.5 30.0+6 0.0 +0.5 0.05. Simulation conventionsIt should be noted that heights for the system stacks are measured positive upwards from the stack base in each case. This implies that entrained airflow towards the stack base is negative. Airflow entering the network from any AAVs installed will therefore be indicated as negative. Airflow exiting the network to the sewer connection will be negative.Airflow entering the network from the sewer connection or induced to flow up any stack will be positive.Water downflow in a vertical is however regarded as positive.Observing these conventions will allow the following simulation to be better understood.6. Water discharge to the networkTable 1 illustrates the w.c. discharges described above, simultaneous from 1s to stacks 1–3 and from 2s to stack 4. A base of stack surcharge is assumed in stack 1 from 2.5 to 3s. As a result it will be seen from Fig. 4 that entrained air downflows are established in pipes 1, 6 and 14 asexpected. However, the entrained airflow in pipe 19 is into the network from the sewer. Initially, as there is only a trickle water flow in pipe 19, the entrained airflow in pipe 19 due to the w.c. discharges already being carried by pipes 1, 6 and 14, is reversed, i.e. up the stack, and contributes to the entrained airflow demand in pipes 1, 6 and 14. The AAV on pipe 12 also contributes but initially this is a small proportion of the required airflow and the AAV flutters in response to local pressure conditions.Fig.4.Entrained airflows during appliance discharge.Following the w.c. discharge to stack 4 that establishes a water downflow in pipe 19 from 2 s onwards, the reversed airflow initially established diminishes due to the traction applied by the falling water film in that pipe. However, the suction pressures developed in the other three stacks still results in a continuing but reduced reversed airflow in pipe 19. As the water downflow in pipe 19 reaches its maximum value from 3 s onwards, the AAV on pipe 12 opens fully and an increased airflow from this source may be identified. The flutter stage is replaced by a fully open period from 3.5 to 5.5 s.Fig. 5 illustrates the air pressure profile from the stack base in both stacks 1 and 4 at 2.5 s into the simulation. The air pressure in stack 4 demonstrates a pressure gradient compatible with the reversed airflow mentioned above. The air pressure profile in stack 1 is typical for a stack carrying an annular water downflow and demonstrates the establishment of a positive backpressure due to the water curtain at the base of the stack.Fig.5.Air pressure profile in stacks 1 and 4 illustrating the pressure gradient driving the reversed airflow in pipe 19.The initial collapsed volume of the PAPA installed on pipe 13 was 0.4l, with a fully expanded volume of 40l, however due to its small initial volume it may be regarded as collapsed during this phase of the simulation.7. Surcharge at base of stack 1Fig. 6 indicates a surcharge at the base of stack 1, pipe 1 from 2.5 to 3 s. The entrained airflow in pipe 1 reduces to zero at the stack base and a pressure transient is generated within that stack, Fig.6. The impact of this transient will also be seen later in a discussion of the trap seal responses for the network.Fig.6.Air pressure levels within the network during the w.c. discharge phase of the simulation. Note surcharge at base stack 1, pipe 1 at 2.5s.It will also be seen, Fig. 6, that the predicted pressure at the base of pipes 1, 6 and 14, in the absence of surcharge, conform to that normally expected, namely a small positive back pressure as the entrained air is forced through the water curtain at the base of the stack and into the sewer. In the case of stack 4, pipe 19, the reversed airflow drawn into the stack demonstrates a pressure drop as it traverses the water curtain present at that stack base.The simulation allows the air pressure profiles up stack 1 to be modelled during,and following, the surcharge illustrated in Fig. 6. Fig. 7(a) and (b) illustrate the air pressure profiles in the stack from 2.0 to 3.0 s, the increasing and decreasing phases of the transient propagation being presented sequentially. The traces illustrate the propagation of the positive transient up the stack as well as the pressure oscillations derived from the reflection of the transient at the stack termination at the AAV/PAPA junction at the upper end of pipe 11.Fig.7.(a) Sequential air pressure profiles in stack 1 during initial phase of stack base surcharge. (b) Sequential air pressure profiles in stack 1 during final phase of stack base surcharge.8. Sewer imposed transientsTable 2 illustrates the imposition of a series of sequential sewer transients at the base of eachstack. Fig. 8 demonstrates a pattern that indicates the operation of both the PAPA installed on pipe 13 and the self-venting provided by stack interconnection.Fig.8.Entraind airflows as a result of sewer imposed pressure transients.As the positive pressure is imposed at the base of pipe 1 at 12 s, airflow is driven up stack 1 towards the PAPA connection. However, as the base of the other stacks have not a yet had positive sewer pressure levels imposed, a secondary airflow path is established downwards to the sewer connection in each of stacks 2–4, as shown by the negative airflows in Fig. 8.As the imposed transient abates so the reversed flow reduces and the PAPA discharges air to the network, again demonstrated by the simulation, Fig. 8. This pattern repeats as each of the stacks is subjected to a sewer transient.Fig. 9 illustrates typical air pressure profiles in stacks 1 and 2. The pressure gradient in stack 2 confirms the airflow direction up the stack towards the AAV/PAPA junction. It will be seen that pressure continues to decrease down stack 1 until it recovers, pipes 1 and 3, due to the effect of the continuing waterflow in those pipes.The PAPA installation reacts to the sewer transients by absorbing airflow, Fig. 10. The PAPA will expand until the accumulated air inflow reaches its assumed 40 l volume. At that point the PAPA will pressurize and will assist the airflow out of the network via the stacks unaffected by the imposed positive sewer transient. Note that as the sewer transient is applied sequentially from stacks 1–4 this pattern is repeated. The volume of the high level PAPA, together with any others introduced into a more complex network, could be adapted to ensure that no system pressurization occurred.Fig.9.Air pressure profile in stack 1 and 2 during the sewer imposed transient in stack 2, 15s into the simulation.Fig.10.PAPA volume and AAV throughflow during simulation.The effect of sequential transients at each of the stacks is identifiable as the PAPA volume decreases between transients due to the entrained airflow maintained by the residual water flows in each stack.9. Trap seal oscillation and retentionThe appliance traps connected to the network monitor and respond to the local branch air pressures. The model provides a simulation of trap seal deflection, as well as final retention. Fig. 11(a,b) present the trap seal oscillations for one trap on each of the stacks 1 and 2, respectively. As the air pressure falls in the network, the water column in the trap is displaced so that the appliance side water level falls. However, the system side level is governed by the level of the branch entry connection so that water is lost to the network. This effect is illustrated in both Fig. 11(a) and (b).Transient conditions in the network result in trap seal oscillation, however at the end of the event the trap seal will have lost water that can only be replenished by the next appliance usage. If the transient effects are severe than the trap may become totally depleted allowing a potential cross contamination route from the network to habitable space. Fig. 11(a) and (b) illustrate the trap seal retention at the end of the imposed network transients.Fig.11.(a) Trap seal oscillation, trap 2. (b) Trap seal oscillation, trap 7.Fig. 11(a), representing the trap on pipe 2, illustrates the expected induced siphonage of trap seal water into the network as the stack pressure falls. The surcharge event in stack 1 interrupts this process at 2s. The trap oscillations abate following the cessation of water downflow in stack 1. The imposition of a sewer transient is apparent at 12s by the water surface level rising in the appliance side of the trap. A more severe transient could ha ve resulted in ‘bubbling through’ at this stage if the trap system side water surface level fell to the lowest point of the U-bend.The trap seal oscillations for traps on pipes 7, Fig. 11(b) and 15, are identical to each other until the sequential imposition of sewer transients at 14 and 16s. Note that thesurcharge in pipe 1 does not affect these traps as they are remote from the base of stack 1. The trap on pipe 20 displays an initial reduction in pressure due to the delay in applied water downflow. The sewer transient in pipe 19 affects this trap at around 18s.As a result of the pressure transients arriving at each trap during the simulation there will be a loss of trap seal water. This overall effect results in each trap displaying an individual water seal retention that depends entirely on the usage of the network. Trap 2 retains 32mm water seal while traps 7 and 15 retain 33mm. Trap 20 is reduced to 26mm water seal. Note that the traps on pipes 7 and 15 were exposed to the same levels of transient pressure despite the time difference in arrival of the sewer transients. Fig. 11(a) and (b) illustrate the oscillations of the trap seal column as a result of the solution of the trap seal boundary condition, Eq. (10), with the appropriate C+ characteristic. This boundary condition solution continually monitors the water loss from the trap and at the end of the event yields a trap seal retention value. In the example illustrated the initial trap seal values were taken as 50mm of water, common for appliances such as w.c.'s and sinks.10. Conclusion—viability of a sealed building drainage and vent systemThe simulation presented confirms that a sealed building drainage system utilizing active transient control would be a viable design option. A sealed building drainage system would offer the following advantages:• System s ecurity would be immeasurably enhanced as all high-level open system terminations would be redundant.• System complexity would be reduced while system predictability would increase.• Space and material savings would be achieved within the construction ph ase of any installation.These benefits would be realized provided that active transient control and suppression was incorporated into the design in the form of both AAV to suppress negative transients and variable volume containment devices (PAPA) to control positive transients.The diversity inherent in the operation of both building drainage and vent systems and the sewers connected to the building have a role in providing interconnected relief paths as part of the system solution.The method of characteristics based finite difference simulation presented has provided output consistent with expectations for the operation of the sealed system studied. The accuracy of the simulation in other recent applications, including the accurate corroboration of the SARS spread mechanism within the Amoy Gardens complex in Hong Kong in 2003, provides a confidence level in the results presented.。
建筑给排水英文文章
建筑给排水英文文章一、IntroductionIn the field of architecture, plumbing systems play a crucial role in providing clean water and removing waste from a building. Effective and efficient building plumbing systems are essential for the health and safety of occupants. This article will explore the various aspects of building plumbing systems, including design principles, materials used, installation methods, and maintenance requirements.二、Design PrinciplesA well-designed plumbing system in a building relies on several key principles:1. Water Supply DesignThe design of a water supply system involves determining the source of water, calculating the required flow rate, and sizing the pipes accordingly. Factors such as building size, occupancy, and water demand must be considered. Additionally, backflow prevention devices are installed to prevent contamination of the water supply.2. Drainage System DesignThe drainage system design focuses on removing wastewater from the building and ensuring proper disposal. Gravity is commonly used to move wastewater through a series of pipes and drains. Proper slope, pipe diameter, and venting are important considerations to prevent blockages, odors, and sewer gas leaks.3. Fixture LayoutThe layout of plumbing fixtures, such as sinks, toilets, and showers, should be carefully planned to optimize water usage, convenience, andaccessibility. Adequate space and accessibility for maintenance should be considered during the design phase.三、Materials UsedVarious materials are used in the construction of plumbing systems. The choice of materials depends on factors such as the type of water supply, budget, and local regulations. Common materials used include:1. PipesPipes are typically made of materials such as copper, galvanized steel, PVC (polyvinyl chloride), and PEX (cross-linked polyethylene). Each material has its advantages and disadvantages, such as durability, cost, ease of installation, and resistance to corrosion.2. Fittings and ValvesFittings and valves connect and control the flow of water within the plumbing system. They are available in materials like brass, copper, and plastic. The choice of fittings and valves depends on the specific requirements of the system and its intended use.四、Installation MethodsProper installation of plumbing systems is crucial to ensure their functionality and longevity. Different installation methods are used depending on the building structure and plumbing system design. Some common installation methods include:1. Traditional Open-Cut MethodThis method involves excavating trenches for the placement of pipes. It allows for easy access and repair but can be time-consuming and disruptive, especially in existing buildings.2. Trenchless TechnologyTrenchless technology, such as pipe bursting and pipe lining, is gaining popularity due to its minimal disruption and cost-effectiveness. It involves using specialized equipment to repair or replace pipes without the need for extensive excavation.五、Maintenance RequirementsRegular maintenance is essential to keep building plumbing systems in optimal condition. Neglecting maintenance can lead to leaks, blockages, and water damage. Some important maintenance requirements include:1. Regular InspectionsPeriodic inspections of the plumbing system can help identify any potential issues before they escalate into costly repairs. Inspections should include checking for leaks, proper drainage flow, and functioning of valves and fixtures.2. Clearing BlockagesBlockages in drains and pipes should be promptly cleared to prevent backups and plumbing system failures. This may involve using mechanical tools or chemicals, depending on the nature of the blockage.3. Water Heater MaintenanceWater heaters should be inspected and serviced regularly to ensure efficient and safe operation. This includes checking for leaks, sediment buildup, and testing the pressure relief valve.六、ConclusionBuilding plumbing systems are vital for the functionality and comfort of a building. Proper design, choice of materials, installation methods, and regular maintenance are key factors in ensuring the performance and longevity of these systems. By following the principles discussed inthis article, architects, engineers, and building owners can createreliable and efficient plumbing systems that meet the needs of occupants while adhering to relevant regulations.。
给排水工程屋顶排水中英文对照外文翻译文献
中英文对照外文翻译(文档含英文原文和中文翻译)Short and Long Term Advantage roof drainage design performance Decade has witnessed great changes in the design of the roof drainage system recently, particularly, siphon rainwater drainage system has been gradually improved, and there is likely to be the key application. At the same time these changes, urban drainage system design has undergone tremendous changes, because the scope of a wider urban drainage system design for sustainable development, as well as people for climate change flooding more attention. The main contents of this article is how to design roof drainage systems and make a good performance. Special attention is how to get rid of bad habits already formed the design, but also need to consider innovative roof drainage system, such as green roofs and rainwater harvesting systems.Practical application: In the past few years, the design of the roof rainwater drainage system has undergone tremendous changes. On large buildings, siphon rainwater drainage technology has been very common, as well as green roofs because it is conducive to green development, being more and more applications. Taking into account the ongoing research, this article focuses on how to effectively design a variety of roof rainwater drainage system, and make it achieve the desired design effect.1. IntroductionIn the past decade, the city and the water drainage system design has been widely accepted thinking about sustainable urban drainage system, or the optimal management direction. The main principles of the design of these systems is both a local level in line with the quality of development, but also to create some economic benefits for the investors. This principle has led to the development of new changes in the sump. Although the application of such a device isgradually reduced, but the urban environment relatively high demand areas still require 100% waterproof and rapid drainage, such as the roof. Typically roof drainage system in the design, construction and maintenance has not been given due attention. Although the drainage system investment costs account for only a small portion of the total construction investment, but not able to judge the loss caused by poor design.There are two different forms of roof drainage system design methods, namely the traditional and siphon method. Traditional systems rely on atmospheric pressure work, the drive ram affected sink flow depth. Therefore, the conventional roof drainage systems require a relatively large diameter vertical drop tube, prior to discharge, all devices must be connected to the groundwater collection pipe network. In contrast, siphonic roof drainage pipe systems are generally designed to full flow (turbulent flow means that require less exhaust pipe), which will form a negative pressure, the larger the higher flow rate and pressure head. Typically siphon system requires less down pipe work under negative pressure to the water distribution network can mean higher altitude work, thereby reducing the amount of underground pipe network.Both systems consists of three parts: the roof, rainwater collection pipes, pipe network.All of these elements are able to change the water pressure distribution system. This section focuses on the role and performance of each part. Due to the principle of siphon system has not been well understood, resulting argument is relatively small, this article will highlight siphon system.2. RoofThe roof is usually designed by the architect, designer and not by the drainage design. There are three main roof.2.1 Flat roofFlat roofs are used in industrial buildings less rainfall regions and countries. This roof is not completely flat, but lower than the minimum roof slope may require. For example, the United Kingdom require maximum slope of 10 °. Setting minimum slope in order to avoid any unnecessary water.Despite the flat roof if it is not properly maintained will have more problems, but it will reduce the dead zone within the building, and the ratio of sloping roofs in favor of indoor air.2.2 sloping roofsMost residential and commercial buildings are pitched roof, inclined roof is the biggest advantage can quickly drain, thereby reducing leakage. In temperate regions, we need to consider carrying roof snow load. Once it rains, rainfall through the sloping roofs can be determined by calculation. When rainfall data can be used, you can use the kinematic theory to solve such problems.2.3 green roof (flat or inclined)It can prove roof is the oldest green roofs, including rainfall can reduce or disperse roof planted with plants. It can be planted with trees and shrubs roof garden, it can also be a vegetated roof light carpet. Wherein the latter technique has been widely used. Some of these applications tend to focus on aesthetic requirements and are often used in green development. Since the aesthetic requirements and pressure requirements, as well as green roofs thermal insulation function, reduce the heat island effect, silencer effect, extend the life of the roof.Green roofs in Germany, the most widely used, followed in North America, but to consider the impact on the aesthetics. Germany is by far the most experienced countries in the 19th centuryhave practical application, then as an alternative to reduce the risk of fire tar roof an option in urban areas. Germany is currently the main research question on the cultivation of other issues to consider smaller cities. A study from 1987 to 1989, was found packed with 70 mm thick green roof can be reduced by 60% -80% of heat loss. In a Canadian work computer model based on the roof indicates that as long as the sump, the area can reach 70% of the roof area can be reduced by 60 percent in one year, the same model was also used for artificial rainfall, which the results indicate that rainfall in the catchment season helps to drain away rainwater.However, none of these studies show that green roofs can play a useful role in the rainfall season, or how high collection efficiency of water supply. The United States did some tests, as long as the green roofs regular watering, can reduce 65 percent of the runoff in a rainfall. America's most authoritative green roof guidelines by the New Jersey state environmental agencies promulgated. The main principle is to solve the structural problems of light, and how can the normal drainage after two years.Rainfall period is based on the probability of failure is determined. The system is typically based on rainfall during rainstorms two minutes, two minutes, have a choice. Although this model will get more traffic, but there is no other better alternative. Studies have shown that the traditional model is applied to study green roofs are premature.Loss factor than traditional roof records should be small, about 98.7%.Peak flow will be reduced, although not penetrate, the surface roughness but also have a significant impact.Concentrated rainfall than two minutes for a long time, especially for large roof areas, such as public buildings, commercial buildings, industrial buildings.Urban drainage design should also consider other factors, for a complex system, a green roof in a rain is not enough. Water flow duration curve shows a longer than traditional systems. And two independent and will affect between is possible, which requires a more precise time period. 3. Rainwater CollectorBasic requirements rainwater collector is designed to be able to accommodate rainfall rainstorms. Although it is possible to make a slightly inclined roof drainage purposes, but the nature of the construction industry and building settlement will become flat roof Typically, the tank is placed in a horizontal, sectional view of the water is outwardly inclined, which the role of hydrostatic.3.1 drain outletAnalyzing rainwater collector has sufficient volume is the key to the sump outlet external setting conditions. Also affect the flow rate into the storm water drainage system piping, but also affect the depth of the water catchment. Although the depth of the sump will not bring any particular problems, but too deep can cause excessive sump.Numerous studies in the 1980s showed that the flow of conventional roof drainage system outlet can be divided into two cases. It depends on the size of the depth and size of the outlet. When the water depth is less than half the diameter of the outlet, the flow of the first type, and the outlet of the flow can be calculated by an appropriate equation; water depth increases, exports are slowly clogging the flow will become another form forms, at the same time, the flow of exports can be obtained through other equations. While conventional roof drainage systems are designed to be free-draining, but may cause limitations encountered in the design of the flow is not free. In this case, it will require additional depth.Siphon roof drainage systems, the outlet is designed to be submerged stream. In this case, the depth of the outlet of the decision is more complicated, because the design of the sump depends on the flow. Recent studies have shown that conventional roof drainage systems use a variety of non-standard catchment, their depth and height, bigger than the diameter of the outlet. This will eventually result in a siphon effect. For a given catchment, the flow depends on the starting end of the drop tube diameter. A similar phenomenon has also been used to study the standard catchment, in these circumstances, only limited siphon action occurs within relatively close distance from the exit.3.2 tank flow classificationIn the complex flow sump outlet flow classification, can be seen from Table 2a, the flow will be uniform layering, regardless of whether the same inlet flow. Table 2b and 2c show, export distribution will greatly influence the flow.When the outlet is not a free jet, sump outlet complex flow classification is difficult to describe. Because each catchment tank pressures are likely to be merged. For example, the siphon tube system design point is at near full jet outlet flow classification depends on the energy loss of each branch.3.3 hydrostatic sectionalSump shape of the water surface in the canal can be classified according to the flow equation. In most cases, a low flow rate means that there is less friction loss, if exports are free jet, the friction loss is negligible cross-section through the hydrostatic equation 1 to determine the horizontal distance.Where Q-- flow (m3 / s)T- surface width (m)g- acceleration of gravity (m / s2)F- flow area (m2)Equation 1 can not be ignored when the friction required to correct (or very long pipe velocity is large), or not a free jet.3.4 The current design methodsThe previous discussion has highlighted the main factors that should be considered with sink design. However, without the help of a certain number of models, computing hydrostatic sectional roof drainage system, the volume of the sump is possible. This large commercial and manufacturing industry, is a development opportunity, you can merge several kilometers of water routes. Thus, the conventional drainage system sump design methods are mainly based on experience, and assume that exports are free jet.Sump location in the building, it may cause the example to fail.Different interface sumpExcept in the case cited above, but also allows designers to use empirical data.3.5 Digital ModelLarge number of digital models can be used to accurately describe the flow of any form of catchment tank, regardless of whether the roof flows stable. An example of this model is a combination of roof space model. This model enables users to classify different aspects of the data indicated, includes: details of the rains, the roof surface drainage and other details. Kinematics have also been used to study rainwater tank to flow from the research collection. A typical method is based on open system to solve a basic problem of spatial mobility. This model automaticallyresolve the sump outlet flow situation, but also to deal with the case of free jet can also be simulated space limited mobility and submerged discharge. Output values include depth and flow rate.Currently, the model is essentially just a variety of research tools, but also through practical engineering test. However, we should face up to the various role models.4 pipe systems groupComposition in the form and scope of the tube group determines the roof drainage system relies mainly on the traditional system or siphon action.4.1 Traditional stormwater systemsConventional roof drainage systems, the ground plane is generally vertical pipe-line network, connected to the sump outlet and underground drainage systems, critical systems as well as compensating tube. It should be emphasized that the angle between the ground and the compensating tube is less than 10 °. Capacity of the entire system relies mainly on the outlet tube instead of down.Flow vertical tube is usually free-flowing, full of only 33%, the efficiency depends on the excess length of the tube. If the drop tube long enough (typically greater than 5m), there may be an annular flow. Similarly, under normal circumstances flow compensation pipe is free-flowing, full of up to 70%. Such designed process both for the design, various equations can also be used.4.2 Siphon roof drainage systemIn contrast with the traditional drainage systems, Siphon roof drainage system relies on air flow outside the system, and the tube is full pipe flow stream.The designs are usually made on the assumption that the design of heavy rain, the system can quickly siphon discharge rainwater. This assumption allows the application of hydrostatic siphon system theory. Often used steady flow energy equation. While this approach ignores the small amount of energy loss at the entrance, but after the experiment showed that there are still conducive to practical use.However, steady-state design methods in the siphon system is exposed to rain when the system does not meet the standard requirements or changes in rainfall intensity is large is not applied. In the first case, there will be some mixing of air quality, annular flow occurs. These problems are not integrated in the system when more serious. Because usually designed rains are common, it is clear now design methodology over time may not apply to siphon system. This is a major disadvantage, because the design of the main problem is the noise and vibration problems.Despite the disadvantages of the prior design approach, but a lot of the world's very few engineering failure reports. When a failure occurs, most likely for the following reasons: An incorrect understanding of the operation pointsSubstandard materials listInstallation defectsMaintenance mismanagementTo overcome these disadvantages, we have recently launched a series of research projects, to discuss the siphon system, and the development of digital models. From this work we learn a lot. In contrast with conventional design methods of some assumptions, siphon system mainly has the following aspects:1) non-flow system of full flow2) levels of certain pipe-flowing full pipe flow3) full pipe flow downstream propagation through a vertical pipe, riser, etc.4) the inner tube flow occurs over the vertical section, the system to reduce the pressure5) downward tube is full pipe flow, there will be air lock6) appears completely siphon action until well into the air system is lower than a certain levelTable 4a column data indicate that below the design point, the system will siphon unstable flow, depth of the water collecting tank is insufficient to maintain the siphon action. Table 4b show that the unsteady flow in siphon system when it will appear.Table 5 lists the data output of a digital model. It can be seen that the model can accurately describe the siphon action, siphon and steady state, the data also show that the model can accurately describe the complex siphon action.5 ConclusionThis article has illustrated the critical roof drainage systems, but these are often overlooked in the urban drainage system design. This article also shows that the design process is a complex process, rely mainly on the performance of exports. The following conclusions are based on the design summed up:1) Run depend on three interacting parts: the roof, sump, water pipes2) Green roofs can reduce traffic and beautify the city3) the export performance of the system is essential4) siphon drainage system have a greater advantage in large-scale projects, but must be considered high maintenance costs5) Design siphon drainage system should consider additional capacity and operational issuesAlthough the green roof is a more attractive option, but the traditional roof of a building in the country will continue to dominate. Green roofs will be gradually developed, and gradually been widely accepted. Similarly, the roof drainage system shown effective that it will continue to play a huge role in the commercial building drainage systems.Roof drainage system of the greatest threats from climate change, existing systems tend to be not simply aging; rainfall patterns of change will result in inefficient operation, self-cleaning rate will be reduced. Changes in wind speed and the roof will also accelerate the aging of the roof, it is necessary to carry out maintenance. Taking into account the climate change, the increase in materials, roof collected rainwater will be more extensive. Currently, the amount of rain around the globe per person per day 7-300 liters in the UK, with an average consumption of 145L / h / d, of which only about one liter is used by people, about 30 per cent of the toilet, study shows If water shortage, rainwater collected on the roof of developed and developing countries are recommended approach.屋顶排水设计性能的近期与远期优势最近十年见证了屋顶排水系统设计方面的巨大变化，特别的是，虹吸雨水排水系统已经得到逐步改善，并且有可能得到重点应用。
给排水专业英文文献翻译
Key words: Sewage treatment, fixed-film and suspended-growth, Activated sludge Origins of sewage Sewage is created by residences, institutions, and commercial and industrial
stream, river, bay, lagoon or wetland, or it can be used for the irrigation of a golf
course, green way or park. If it is sufficiently clean, it can also be used for
waste stream (or treated effluent) and a solid waste or sludge suitable for discharge or
reuse back into the environment. This material is often inadvertently contaminated
Conventional sewage treatment may involve three stages, called primary,
secondary and tertiary treatment. Primary treatment consists of temporarily holding
(effluents) and domestic. It includes physical, chemical, and biological processes to
给水排水中英文对照外文翻译文献
中英文对照外文翻译文献(文档含英文原文和中文翻译)原文：Optimum combination of water drainage,water supply and eco-environment protection in coal-accumulated basin of North ChinaAbstract The conflict among water drainage,water supply and eco-environment protection is getting more and more serious due to the irrational drainage and exploitation of ground water resources in coal-accumulated basins of North China.Efficient solutions to the conflict are tomaintain long-term dynamic balance between input and output of theground water basins,and to try to improve resourcification of the mine water.All solutions must guarantee the eco-environment quality.This paper presents a new idea of optimum combination of water drainage，water supply and eco-environment protection so as to solve theproblem of unstable mine water supply,which is caused by the changeable water drainage for the whole combination system.Both the management of hydraulic techniques and constraints in economy,society,ecology,environment,insustuial structural adjustments and sustainable developments have been taken into account.Since the traditional and separate management of different departments of water drainage,water supply and eco-environment protection is broken up these departments work together to avoid repeated geological survey and specific evaluation calculations so that large amount of national investment can be saved and precise calculation for the whole system can be obtained.In the light of the conflict of water drainage,water supply and eco-environment protection in a typical sector in Jiaozuo coal mine,a case study puts forward an optimum combination scheme,in which a maximum economic benefit objective is constrained by multiple factors.The scheme provides a very important scientific base for finding a sustainable development strategy.Keywords combination system of water drainage,water supply and eco-environment protection,optimal combination,resourcification of mine water.1Analyses of necessity for the combinationThere are three related problems in the basin.It is well known that the major mine-hydrogeological characteristics of the coal accumulated basin in North China display a stereo water-filling structure,which is formed by multi-layer aquifers connected hydraulically together with various kinds of inner or outer boundaries.Mine water hazards have seriously restricted the healthy development of coal industry in China because of more water-filling sources and stronger water-filling capacity in coal mines of the basin.Coal reserves in the basin are threatened by the water hazards.In Fengfeng,Xingtai,Jiaozuo,Zibao,Huaibei and Huainan coal mine districts,for example,it is estimatedthat coal reserves are threatened by the water hazards up to 52％,71.％40,％,60％,48％and 90％of total prospecting reserves respectively.It is obvious that un-mining phenomenon caused by the water hazards is serious.Water-bursting accidents under coal layers have seriously influenced safe production.Some statistical data show that there were 17 water-bursting accidents with over 1 m3/s inflow from 1985.Water drainage is an increasing burden on coal mines threatened by water hazards:high cost of water drainage raises coal prices and reduces profits of the enterprise.On the other hand,it is more and more difficult to meet the demand of water supply in coal mine districts in the basin.The reasons are not only arid and semi-arid weather conditions,but also a large amount of water drainage with deep drawdown in coal mines and irrational water exploitation.The deterioration of eco-environment is another problem.Phenomena of land surface karst collapse can be found.Many famous karst springs,which are discharge points for the whole karst groundwater syatem,stop flowing or their discharge rates decrease on a large scale.Desert cremophytes in large areas in west China die because of falling groundwater level.These three problems are related and contradictory.In order to solve the problems while ensuring safe mining,meeting water resource demands and slowing down the pace of eco-environment deterioration,it is necessary to study the optimum combination of water drainage,water supply and eco-environment protection in the basin.2The state of the art of research and the problemsAlthough research into the combination of water drainage and water supply started much earlier in some countries,their conception is simple and some shortcomings remain in their study on the theory and pattern of combination.China’s research history on the combination can be divided into three stages.The first stage is the utilization of mine water.A century ago mine water started to be used as water supply for mines.But the utilization scale and efficiency were quite limited at that time.The second stage is a comprehensive one:mine water was used while water hazards were harnessed.Great progress was made both in theory and practice of the combination.For example,the combination of water drainage and water supply not only means the utilization of mine water,but also means that it is a technique of preventing water hazards.It is unfortunate,however,that the combination research in this stage offered less sense ofeco-environment protection.Optimum combination management of water drainage,water supply and eco-environment protection is the third stage.Main features in this stage are to widen traditional research,and to establish an economic-hydraulic management model,in which safe mining,eco-environment protection and sustainable development demands,etc.are simultaneously considered as constraint conditions.3Trinity systemThe trinity system combines water drainage,water supply and eco-environment quality protection.The water-collecting structures of the system consist of land surface pumping wells in the mines,shallow land surface well in groundwater recharge areas and artificial relief wells under the mines.Both integration and coordination for the trinity system are distinguished according to the combination.The integration for the system means to utilize drainage water under the mines and pump water onto the land surface as water supply for different purposes without harming the eco-environmental quality.The coal mines are not only drainage sites,but also water supply sources.The purpose of drilling pumping wells on the land surface is to eliminate special influences on different consumers,which are caused by terminating drainage processes under the mines due to unexpected accidents in mining.The coordination for the system means to bulid some water supply sources for different consumers while ensuring eco-environmental quality in groundwater recharge positions,where pumping groundwater is quite effective on lowering groundwater heads in the mine areas.Itintercepts in advance the recharging groundwater flow towards the mines,which may not only provide consumers with good quality groundwater,achieve the goal of dropping down groundwater heads in the mines,but also effectively reduce the high costs of drainage and water treatment,which are needed by traditional dewatering measures with large drainage flow rates under the mines.The coordination changes the traditional passive pattern of preventing and controlling groundwater hazards under the mines into that of active surface interception.Both very developed karst flow belts and accumulated groundwater recharge ones under the ground are relatively ideal interceptive coordination positions in the system.For the integration of the trinity system,artificial relief wells under the mines and the land surface pumping wells mainly penetrate into direct thin bedded karst aquifers interbedded with the mining coal layers,while for the coordination of the system,the shallow land surface wells mainly penetrate into very thick karst aquifer.Therefore,hydrogeological conceptual model for the system involves the multi-layer aquifers connected hydraulically by different inner boundaries.Setting up stereo hydrogeological conceptual models and corresponding mathematical models is a prerequisite for solving the managemental problems for the system.Management of the trinity system not only considers the effects of lowering groundwater heads and safe operation for water drainage subsystem,but also pays attention to the water demands for water supply subsystem and quality changes for eco-environment protection subsystem.They play the same important role in the whole combination system.It controls the groundwater heads in each aquifer to satisfy the conditions of safe mining with certain water head pressures in the mines,and to guarantee a certain amount of water supply for the mines and near areas,but the maximum drawdown of groundwater must not be ex ceded,which may result in lowering eco-environmental quality.4Economic-hydraulic management modelIn the trinity system management,groundwater resources in the mines and nearby areas,which are assessed on the premise of eco-environment qualities and safe operation in the mines,may be provided as water supply prices,drainage costs,transportation costs(including pipeline and purchasing the land costs)and groundwater quality treatment costs for the three different waterconsumers,the optimum management models may automatically allocate to each consumer a certain amount of groundwater resources and a concrete water supply scenario based on comparisons of each consumer’s economic contribution to the whole system in objective function.Therefore the management studies on the optimal combination among water drainage,water supply and eco-environment protection involve both the management of groundwater hydraulic techniques and the economic evaluations,eco-environment quality protection and industrial structure programs.In addition to realizing an economic operation,they also guarantee a safe operation which is a key point for the combination of the whole system.5The management model for the trinity system can reach water supply goals with drainage water under the mines and the land surface pumping water on the premise of ensuring eco-environmental quality.And it can make use of one model to lay down comprehensively optimum management scenarios for each subsystem by means of selecting proper constraints and maximum economic benefit objective produced by multiple water consumers.The model can raise the security and reliability of operation for the whole trinity system,and the drainage water can be forecast for the mines and the management of water supply resource and the evaluation of eco-environment quality can be performed at the same time so as to respectively stop the separate or closed management,of departments of drainage water,water supply and eco-environment protection from geological survey stage to management evaluation.This,in economic aspect,can not only avoid much geological survery and special assessment work which are often repeated by the three departments,and save a lot of funds,but also ,in technical aspect,make use of one model to simultaneously consider interference and influence on each other for different groundwater seepage fields so as to guarantee calculating precision of the forecast,the management and the evaluation work.The economic-hydraulic management model can be expressed as follows.6 A case studyA typical sector is chosen.It is located in the east of Jiaozuo coal mine,Henan Province,China.Itconsists of three mines:Hanwang Mine,Yanmazhuang Mine and Jiulishan Mine.The land surface is flat,and the whole area is about 30 km2.An intermittent river Shanmen flows through the sector from the north to the south.Average annual precipitation in the sector is about 662.3mm.Theprecipitation mainly concentrates inJune,July,August and September each year.Strata in the sector consist of very thick limestone in Middle Ordovician,coal-bearing rock series in Permo Carboniferous and loose deposits in Quaternary.There are four groups of faulted structures.The first is in northeast-southwest direction such as F3 and F1..The second is in the northwest-southeast direction such as Fangzhuang fault.The third is in the east-west direction such as Fenghuangling fault.The last is almost in north-south.These faults are all found to be normal faults with a high degree of dip angle.Four major aquifers have been found in the sector.The top one is a semi-confined porous aquifer.The next one is a very thin bedded limeston aquifer.The third is a thin bedded limestone aquifer.The last one at the bottom is a very thick limestone aquifer.Objective function of the management model is designed to be maximum economic benefit produced by domestic,industrial and agricultural water supply.Policy making variables of the model are considered as the domestic,industrial and agricultural groundwater supply rates in every management time step,and they are supplied by artificial relief flow wells under the mines,the land surface pumping wells in the mines and the shallow land surface wells in the groundwater recharge areas.All the 135 policy making variables are chosen in the model,27 for drainage wells under the mines in aquifer,27 for the land surface pumping wells in the mine districts in aquifer 27 in aquifer 27 in aquifer O2 27 for the shallow land surface wells in aquifer O2Based on the problems,the following constraint conditions should be considered:(1)Safe mining constraint with groundwater pressure in aquifer L8.There are altogether three coalmines in the typical sector,i.e.Hanwang Mine,Yanmazhuang Mine and Jiulishan Mine.Elevations of mining level for these mines are different because it is about 88-150 m in the second mining level for Hanwang Mine,and -200m in the second mining level for Yanmazhuang Mine,and-225 m in the first mining level for Jiulishan Mine.According to mining experiences,pressure-loaded heights for groundwater heads in safe mining state are considered as about 100-130m.Therefore,the groundwater level drawdowns in the three management time steps for aquifer L8 at three mines have to be equivalent to safe drawdown values at least in order to pervert groundwater hazards under the mines and to guarantee their safe operation.(2)Geological eco-environment quality constraint.In order to prevernt groundwater leakage fromupper contaminater porous aquifer into bottom one and then to seepage further down to contaminate the thin bedded limestone aquifer in the position of buried outcrop,the groundwater heads in the bottom porous aquifer must keep a certain height,i.e.the groundwater drawdowns in it are not allowed to exceed maximum values.(3)Groundwater head constraint at the shallow land surface wells in aquifer O2,The shallow landsurface wells should penetrate in aquifer O2 in order to avoid geological environment hazards,such as karst collapse and deep karst groundwater contamination.Groundwater head drawdowns in aquifer O2 for the shallow land surface wells are not allowed to exceed criticalvalues.(4)Industrial water supply constraint for the groundwater source in aquifer O2 .The rate ofindustrial water supply needed by the planned thermal power plant in the north of the sectoris designed to be 1.5 m3/s according to the comprehensive design of the system in thesector.In order to meet the demands of water,the rate industrial water supply for thegroundwater source in aquifer O2 in every management time step must be equivalent at leastto 1.5 m3/s.(5)Maximum amount constraint of groundwater resource available for abstraction.In order tomaintain the balance of the groundwater system in the sector for a long time and to avoid anyharmful results caused by continuous falling of groundwater head,the sum of groundwaterabstraction in each management time step is not allowed to exceed the maximum amount ofgroundwater resource available for abstraction.Since there is not only water drainage in the mines,but also water supply in the whole combination system,management period for the model is selected from June 1,1978 to May 31,1979,in which annual average rate of precipitation is about 50％.Management time steps for the period are divided into three.The first one is from June to September,the second from October to next January,and the last one from next February to May.According to comprehensive information about actual economic ability,economic development program and industrial structure adjustment in the sector at present and in the near future,and different association forms of water collecting structures among the land surface pumping wells,the shallow land surface wells and artificial relief flow wells under the mines,this paper designs 12 management scenarious,all of which take the safe operation in the trinity system as the most important condition.After making comparisons of optimum calculation results for the 12 scenarious,this paper comes to a conclusion that scenarios is the most ideal and applicable one for the typical sector.This scenario not only considers the effective dewatering advantage of the artificial relief flow wells under the mines and safe stable water supply advantage of the land surface pumping wells,but also pays attention to the disadvantage of low safe guaranty rate for the relief flow wells under the mines for water supply and of large drilling investment in the land surface pumping wells.Meanwhile,eh shallow land surface wells inaquifer O2in this scenario would not only provide water supply for the thermal power plant as planned,but also play an important role in dewatering the bottom aquifer,which is major recharge source of groundwater for the mines.If the drainage subsystem under the mines runs normally,this scenario could fully offer the effective dewatering functions of the artificial relief flow wells under the mines,and makes the trinity system operate normally.But if the drainage subsystem has to stop suddenly because of unexpected accidents,the scenario could still fully utilize the land surface pumping wells and the shallow land surface wells,and increae their pumping rates in order to make up for temporary shortage of water supply for the trinity system and to make its economic losses reduced to a minimum extent.Increasing groundwater abstraction rate for the land surface pumping wells and the shallow land surface wells,in fact,is very favorable for harnessing the water-accidents under the mines and for recovery production of the mines.To sum up,this scenario sets up a new pattern for the combination of water drainage,water supply and eco-environment protection.It solves quite well the conflicts between the low safe guaranty rate and the effective dewatering result for the artificial relief flow wells under the mines.It makes full use of beneficial aspect of the conflicts,and meanwhile compensates for the unbeneficial one by arranging the land surface pumping wells in the coal mine districts.Therefore,this scenario should be comprehensive and feasible.In this scenario,Hanwan Mine,Yanmazhuang Mine and Jiulishan Mine are distributed optimally for certain amount of domestic and industrial water supply,but not for much agricultural water supply.The land surface pumping wells are also distributed for different purposes of water supply.The water supply for the thermal power plant (1.5 m3/s) is provided by the shallow land surface prehensive effects,produced by the above three kinds of water collecting structures,completely satisfy all of the constraint conditions in the management model,and achieve an extremely good economic objective of 16.520551million RMB yuan per year.In order to examine the uncertainty of the management model,12management scenarios are all tested with sensitive analysis.7Conclusion(1)The optimum combination research among water drainage,water supply and eco-environmentprotection is of great theoretical significance and application value in the basin of North China for solving unbalanced relation between water supply and demands,developing new potential water supply sources and protecting weak eco-environment.(2)The combination research is concerned not only with hydraulic technique management but alsowith constraints of economic benefits,society,ecology,environment quality,safe mining and sustainable development in the coal mines.(3)The combination model,for the first time,breaks up the closed situation existing for a longtime,under which the government departments of drainage water,water supply and eco-environment protection from geological survey stage to management evaluation work respectively.Economically,it can spare the repeated geological survey and special assessment work done by the three departments and save a lot of funds;technically,one model is made use of to cover the interference and influence each other for different groundwater seepage fields soas to guarantee a high calculating precision of the forecast,the management and the evaluation work.(4)The management scenario presented in the case study is the most ideal and applicable for thetypical sector.This scenario not only makes full use of the effective dewatering advantages of the artificial relief flow wells under the mines and safe stable water supply advantages of the land surface pumping wells,but also pays attention to the disadvantages of low safe guaranty rate for the relief flow wells under the mines for water supply and of large drilling investment for the land surface pumping wells.References1.Investigation team on mine-hydrogeology and engineering geology in the Ministry ofGeology and Mineral Resources.Investigation Report on Karst-water-filling Mines(inChinese).Beijing:Geological Publishing House,19962.Liu Qiren,Lin Pengqi,Y u Pei,Investigation comments on mine-hydrogeological conditionsfor national karst-water-filling mines,Journal of Hydrogeology and Engineering Geology(in Chinese),19793.Wang Mengyu,Technology development on preventing and curing mine water in coalmines in foreign countries,Science and Technology in Coal(in Chinese),19834.Coldewey,W.G.Semrau.L.Mine water in the Ruhr Area(Federal Republic of Germany),inProceedings of 5th International Mine Water Congress,Leicestershire:Quorn SelectiveRepro Limited,19945.Sivakumar,M.Morten,S,Singh,RN,Case history analysis of mine water pollution,inProceedings of 5th International Mine Water Congress,Leicestershire;Quorn SelectiveRepro Limited,19946.Ye Guijun.Zhang Dao,Features of Karst-water-filling mines and combination betweenwater drainage and water supply in China,Journal of Hydrogeology and EngineeringGeology(in China),19887.Tan Jiwen,Shao Aijun,Prospect analyses on Combination between water drainage andwater supply in karst water basin in northern China,Jounnal of Hebei College ofGeology(in Chinese),19858.Xin Kuide,Yu Pei,Combination between water drainage and water for seriouskarst-water-filling mines in northern China,Journal of Hydrogeology and Engineering Geology(in Chinese),19869.Wu Qiang,Luo Yuanhua,Sun Weijiang et al.Resourcification of mine water andenvironment protection,Geological Comments(in Chinese),199710.Gao Honglian,Lin Zhengping,Regional characteristics of mine-hydrogeological conditionsof coal deposits in China,Journal of Hydrogeology and Engineering Geology(in Chinese),198511.Jiang Ben,A tentative plan for preventing and curing measures on mine water in coal minesin northern China,Geology and Prospecting for Coaofield(in Chinese),1993中国北方煤炭积聚区的最佳组合排水，供水和生态环境保护摘要为了开采中国北方煤炭资源丰富的区域，不合理的排水使排水、供水和保护生态环境之间的冲突日趋严重。
给水排水工程专业英语文献翻译原文第一篇
Abbreviations: ADF, Aerobic Dynamic Feeding, also designated as “feast and famine”; CSTR, Continuous Stirred Tank Reactor; C/N, Carbon to nitrogen ratio; HAc, Acetic acid; HB, Hydroxybutyrate; HBut, Butyric acid; HLac, Lactic acid; HProp, Propionic acid; HV, Hydroxyvalerate; HVal, Valeric acid; HRT, Hydraulic Retention Time; OUR, Oxygen Uptake Rate; PHA, Polyhydroxyalkanoate; qP, Maximum specific polymer storage rate; -qS, Maximum specific substrate uptake rate; SBR, Sequencing Batch Reactor; SRT, Sludge Retention Time; TOC, Total Organic Carbon; VFA, Volatile Fatty Acid; VSS, Volatile Suspended Solid; VSSmax, Volatile Suspended Solids at the time of maximum polymer accumulation; X, Active Biomass; Xi, Initial active biomass concentration; YO2/X, Respiration yield, in Cmmol/Cmmol VFA; YP/S, Polymer storage yield, in Cmmol HA/Cmmol VFA; YX/S, Growth yield in Cmmol X/Cmmol VFA
土木工程给水排水英文文献及翻译-英语论文
土木工程给水排水英文文献及翻译-英语论文土木工程给水排水英文文献及翻译Building drainage of water-saving techniquesWith people's quality of life，the quality and quantity of water are constantly expanding. Implement sustainable water use and protection of water resources from destruction. And access to healthy water, recycling of water, has become the government and the broad masses of the people the focus of attention. All this gave to the construction of drainage works on the design of the many new requirements, water supply advanced technology of the urgent need to accelerate the pace. This paper will explore more of the building for drainage of water-saving technology; we hope to arouse the awareness of water conservation to build water-saving city efforts.Construction of a water-saving project, in addition to the water saving should formulate laws and regulations to strengthen the management and day-to-day publicity and education use price leverage to promote water conservation work, but also take effective measures, to ensure that the construction of water-saving work carried out in-depth and comprehensive. We are aware that the water supply network's coverage, the extension of transmission mains and the construction of the building because arisingfrom the difference in height, will be used to increase the water pressure before the end of ways to protect the most disadvantaged water points will be adequate water supply, This will be a large number of regional supply of high pressure water supply is. Therefore accessories before the water hydrostatic head greater than outflow, the flow was greater than the rated flow capacity. Beyond the rated flow capacity of that part of the normal flow did not have the use efficiency is a waste of water. As a result of this water is being wasted is not easy to detect and understand, it could be called a "stealth" wasting water.It has been in a different type of floor, the building 67 water distribution points so the overpressure from the measured flow analysis, Statistical results are 55% of the iron spiral movements - taps (hereinafter referred to as "ordinary water") and 61% of the ceramic valve - leading the flow of water-saving more than their rated flow, the super-flow pressure from the state. Two endings the largest flow out of the rated flow capacity of about three times [1]. This shows that in our existing buildings, water supply system overpressure out-flow phenomenon is widespread and it is a fairly serious. In distribution point pressure As overpressure flow out of the "invisible" water is not wasted paid enough attention to, So in our existing "building water supply and drainage design" and "construction water supply and drainage design GBJ15-20 00 draft "(hereinafter referred to as" draft "), although the wateraccessories and home support the greatest pressure certain restrictive provisions in [2], but this is only to prevent water from the high pressure parts will lead to damage to the point of consideration, not prevent excess pressure from the out-flow point of view, the pressure is too lenient restrictions on the flow overpressure no fundamental role. Therefore, in accordance with the water supply system overpressure flow from the actual situation, the pressure on the water supply system to make reasonable limit.1.2 measures taken decompressionWater supply system in a reasonable allocation of decompression device is to control pressure within the limits required to reduce excess pressure from the flow of technical support.1.2.1 Jangled nervesRelief valve is a good decompression device, can be divided into proportional (lower left) of direct action and the type (Photo) The former is based on the ratio of the area to determine the proportion of decompression, which can be set under pressure prior decompression, When the water-stop water, you can also be controlling the vacuum tube pressure is not increased, Decompression can achieve dynamic can achieve static decompression.1.2.2 Decompression orifice and conserving Cypriots1106土木工程给水排水英文文献及翻译Orifice decompression compared with jangled nerves example, the system is relatively simple, less investment, easy management. The practice of some units, water-saving effects are fairly obvious, If Shanghai Jiao tong University in the school bathroom water pipe installation aperture of 5 mm orifice, water-saving about 43%. But decompression orifice only by the dynamic pressure, static pressure can be reduced and the pressure downstream with the upstream pressure and the flow is changed, is not stable enough. In addition, the vacuum orifice plug easy. In better water quality and water pressure more stable, by using [3]. Cutting expenditure and the role of Cypriot advantages and decompression orifice basically are the same. Suitable for the small diameter and accessories installed to use [3].1.3 adopt water-saving leadingA trial showed that the leading Practical water-saving taps and the general state of the full, flow out of the former than the latter out of the flow. That is the same pressure, the leading water conservation has good water saving, water-saving volume in 20% ~ 30% between. And the higher the pressure ordinary tap water from the larger, water-saving is leading the greater the volume of water-saving. Therefore, should the building (especially in the standard water pressure in water distribution points) leading installation of water-saving, reduce water wastage. In 1999 theMinistry of Construction, State Economic and Trade Commission, State Bureau of Building materials apparatuses jointly issued a document "on the elimination of residential buildings behind the products notified" require large and medium-sized cities in new residential prohibit the use of helical-style cast iron nozzle movements, actively adopt "ceramic cartridge faucets" and "common faucet technical conditions of the ceramic cartridge faucets [4]. Since the main building of our school building earlier in the toilet faucet is still an ordinary spiral movement - iron taps. We have often seen leading loosening and tightening the leading difficulty caused by the leakage phenomenon. In fact, there is such a faucet overpressure caused by the "invisible" huge waste of water. Schools should arouse the concern of the relevant departments, from the long-term interests for the use of water-saving new leader, reduce unnecessary losses.2 vigorously develop the construction of water facilities, "watercourse." As the name suggests is not delivered on the waterways clean water is not sullied by sewage contamination. Residents put a wash, bathing, washing clothes and other water washing and flushing water together, after CO., filtration and disinfection, Sterilization, which imported waterway network, for toilet flushing, washing cars, and pouring green, onto the road and other non-drinking purposes. China therefore waterway is also known as miscellaneous water Road. With a watercourse which cubic metersof water, equivalent to the use of one cubic meters of clean water, emit less nearly a cubic meter of sewage and kill two birds with one stone. Water-saving achieved nearly 50% [3]. Therefore, the channel has many of the world's water shortage in cities used extensively.2.1 full use washing wastewater and other quality miscellaneous drainage The existing water facilities built in most hotels, colleges, and the basic source for the bathroom bathing wastewater. For some small units, smaller than bathing wastewater, and discharge time is too concentrated, Water facilities are not stable and adequate source of water. And washing with water wastewater, the use of time more evenly, water treatment and the advantages of relatively good, as a water source, to be fully exploited.2.2 Develop and implement as soon as possible the return to the new water quality standardsThe current construction of water reused implementation of the existing “life miscellaneous water quality standards.” The total coli form standards and the requirements of "sanitary standard for drinking water," the same, compared to the developed countries and the Chinese water standards apply to the swim-minus III also strict standards. This has led to two problems: First, many of the existing water works is less than the standard; 2 are fulfilled with a certain degree of difficulty, improvethe water project investment and processing cost. So should develop appropriate indicators of the value of water works to promote the spread土木工程给水排水英文文献及翻译and popularize. Water Saving water is not limiting, or even prevents the water. But reasonable people to water, efficient use of water and not waste. As long as we pay attention to fit the family's bad habits, we will be able to water-saving around 70% [3]. Water and waste a lot of the habits, such as: flush toilets single wash cigarette butts and broken fine waste; to access a cup of cold water. Many people will not venting water; spend the potatoes, carrots after peeling, washing or after the optional vegetables; when the water stopped (open access customers, answer the phone, change TV channels), not turning off the tap; During the suspension, forget turning off the tap; toilets, wash, brush, let the water has been flowing; Before sleep, go out, do not check the faucet; equipment leaks, not promptly repaired. From the following table, we can see in many parts of life as long as we interested to note that the conservation of water is very impressive.3 to promote the use of water-saving devicesIn addition to the family of water-saving attention to cultivate good habits of water, using water-saving devices is very important and also the most effective. Some people prefer laissez-faire, but also refusedto replace water-saving devices, in fact, so much water is a long time down the uneconomical. Thus vigorously promote the use of water-saving devices is the construction of water-saving important ways and means.3.1Water-saving taps3.1.1 Water Saving leading CeramicsCurrently most of the water-saving taps used Ceramics taps. Such taps compared with ordinary taps, water was typically up to 20% ~ 30%; and other types of water-saving compared to the leading and cheap [3]. Therefore, in the residential buildings of architectural vigorously promote the use of such water-saving lead. We taught the fifth floor of the dormitory building and are used by such leading.3.1.2 Closed since delay tapsSince the delay in the water taps closed after a certain time, shut down automatically to avoid Changliushui phenomenon. Water timing to be in a certain range adjustment, both for the convenience of Health has complied with the water-saving requirements suitable for washing in public places with.3.1.3 Photoelectric controlled tapsClosed since the delay of water-saving taps but water while fixed time and meet the different requirements of the use of the object. Photoelectric controlled taps will be able to overcome the above drawbacks, such as the latest one of the type of infrared device control wash, Thefirst installation will be self-inspection of the device in front of or below the fixed reflectors (for example, vanity) and based on the reflectors adjust their distance from work to avoid the past because of automatic water obstacles closer to the front of regular water, Such intelligent device can wash your hands although below action without washing their hands without water. a long time will wash water and do not have long-term can also regularly flush Water Seal failure to avoid a supply shortage ahead of the police [3].3.2The total water-saving flush3.2.1 Use of small volume cisterns commodeChina is promoting the use of water tanks 6 L fecal water-saving devices, and have flushing water to 4.5 L or even less, stood on the stool available. However, we should also pay attention to the drainage system to ensure the normal work of the use of small volume cisterns commode, otherwise they will be brought to plug the pipeline, not a net wash, and other issues. Two respectively flushing cisterns in urine, flushing water for 4 L (or less); Washing stool, Chong stood at 9 L (or less) [3]. (Map is a two-valve I-Yuan annually to the water tanks, to open the stool below the drain urine when opened above the drain Pictured left is the two-block cisterns switch several forms) Israel's construction regulations require all new buildings to install two respectively wash cisterns. China should also vigorously promoted two respectively cisterns, because one day, thenumber is far higher than the urine stool frequency. To three homes as an example, per person per day for a meeting of feces, urine four times and the use of existing water tanks L 9, day to 135 L of water; 6 L of water use, 90 L of water a day;土木工程给水排水英文文献及翻译and the use of cisterns two respectively, 75 L of water a day, can be seen using two respectively cisterns 9 L 6 L than using more water-saving cisterns [3]. 6 L Yuan annually to the use of water-saving cisterns better results. The use of tanks in two trances another advantage is not right and the replacement of the total drainage system to carry out reform therefore particularly applicable to existing buildings the total replacement of water tanks.3.2.2-washing UrinalThe United States launched the Urinal-washing, which is not water, the stench from the toilets without using utensils, In fact, only in one end Urinal add special "trap" devices, but because the economic, health, water effectively, So popular station.3.2.3Photoelectric control UrinalUrinal photoelectric controls in a number of public buildings installations.3.2.4 Delayed flushing valve closedIt is the use of guide-work principle, water officials directly connected with the water pressure high enough circumstances, can protect the instantaneous flushing commode needs to replace tanks and accessories, installation is simple and easy to use, health, low prices, Water-saving effect of the obvious characteristics [3]. We carpentry center is used for such cleaning.3.3 in hot water systems installed in various forms of water-saving devicesIf installed in public bathrooms limited flow orifice, in the cold, hot water imported pressure balance between the installation of equipment; Installation of low-flow plumbing. Inflatable hot water thermostat and cooling, hot water mixed hydrants.3.4 to further develop various forms of water-saving devices3.4.1 Development of different water taps outSome countries, in different places with different water out of taps, Singapore provides water for washing vegetables pots 6 L / min, shower water 9 L / min; China's Taiwan Province launched the spray-wash special taps, the flow was 1 L / min. In China, various taps most of the rated flow capacity of 0.2 L / s, that is 12 L / min, excessive [4]. Therefore be reasonable to develop taps the rated flow, and gradually installed in different places different from water taps.3.4.2 Vacuum water-saving techniquesTo ensure that sanitary ware and sewer cleaning effect of vacuum technology can be applied to drainage works Most of the air instead of using water, relying on the vacuum of high-speed gas-water mixture, and rapid disposal of the sewage, dirt-gully clean and save water and drain away the effects of dirty air. A complete vacuum drainage system, including: vacuum valve and with a magnitude of suction devices occupants, the closed aqueduct, vacuum collection containers. Vacuum pumps, control equipment and channels and so on. Together with the vacuum generated 40 ~ 5min the negative pressure of sewage pumped to the collection containers, then will collect sewage pump effluent into the municipal sewer. Different types of construction in the use of vacuum technology, the average water-saving exceed 40%. The use of the office building water-saving will rate-70% [2].3.4.3 Development zone leading to the wash waterIn Japan, many families use with the leading water wash, wash all the wastewater into water tanks for back flushing. If the water tank, they can directly turn on the water faucet open. Irrigation water use, it can not only save water but also reduce the costs. At present, the water in China has sales.土木工程给水排水英文文献及翻译随着人民生活质量的提高，对供水量和质的要求正不断扩展.同时实施水的可持续利用和保护，使水资源不受破坏，并能进入良性的水质、水量再生循环，也已成为政府和广大人民群众关注的焦点。
给排水工程外文翻译
Short and Long Term Advantage roof drainage design performance Decade has witnessed great changes in the design of the roof drainage system recently, particularly, siphon rainwater drainage system has been gradually improved, and there is likely to be the key application. At the same time these changes, urban drainage system design has undergone tremendous changes, because the scope of a wider urban drainage system design for sustainable development, as well as people for climate change flooding more attention. The main contents of this article is how to design roof drainage systems and make a good performance. Special attention is how to get rid of bad habits already formed the design, but also need to consider innovative roof drainage system, such as green roofs and rainwater harvesting systems.Practical application: In the past few years, the design of the roof rainwater drainage system has undergone tremendous changes. On large buildings, siphon rainwater drainage technology has been very common, as well as green roofs because it is conducive to green development, being more and more applications. Taking into account the ongoing research, this article focuses on how to effectively design a variety of roof rainwater drainage system, and make it achieve the desired design effect.1. IntroductionIn the past decade, the city and the water drainage system design has been widely accepted thinking about sustainable urban drainage system, or the optimal management direction. The main principles of the design of these systems is both a local level in line with the quality of development, but also to create some economic benefits for the investors. This principle has led to the development of new changes in the sump. Although the application of such a device is gradually reduced, but the urban environment relatively high demand areas still require 100% waterproof and rapid drainage, such as the roof. Typically roof drainage system in the design, construction and maintenance has not been given due attention. Although the drainage system investment costs account for only a small portion of the total construction investment, but not able to judge the loss caused by poor design.There are two different forms of roof drainage system design methods, namely the traditional and siphon method. Traditional systems rely on atmospheric pressure work, the drive ram affected sink flow depth. Therefore, the conventional roof drainage systems require a relatively large diameter vertical drop tube, prior to discharge, all devices must be connected to the groundwater collection pipe network. In contrast, siphonic roof drainage pipe systems are generally designed to full flow (turbulent flow means that require less exhaust pipe), which will form a negative pressure, the larger the higher flow rate and pressure head. Typically siphon system requires less down pipe work under negative pressure to the water distribution network can mean higher altitude work, thereby reducing the amount of underground pipe network.Both systems consists of three parts: the roof, rainwater collection pipes, pipe network.All of these elements are able to change the water pressure distribution system.This section focuses on the role and performance of each part. Due to the principle of siphon system has not been well understood, resulting argument is relatively small, this article will highlight siphon system.2. RoofThe roof is usually designed by the architect, designer and not by the drainage design. There are three main roof.2.1 Flat roofFlat roofs are used in industrial buildings less rainfall regions and countries. This roof is not completely flat, but lower than the minimum roof slope may require. For example, the United Kingdom require maximum slope of 10 °. Setting minimum slope in order to avoid any unnecessary water.Despite the flat roof if it is not properly maintained will have more problems, but it will reduce the dead zone within the building, and the ratio of sloping roofs in favor of indoor air.2.2 sloping roofsMost residential and commercial buildings are pitched roof, inclined roof is the biggest advantage can quickly drain, thereby reducing leakage. In temperate regions, we need to consider carrying roof snow load. Once it rains, rainfall through the sloping roofs can be determined by calculation. When rainfall data can be used, you can use the kinematic theory to solve such problems.2.3 green roof (flat or inclined)It can prove roof is the oldest green roofs, including rainfall can reduce or disperse roof planted with plants. It can be planted with trees and shrubs roof garden, it can also be a vegetated roof light carpet. Wherein the latter technique has been widely used. Some of these applications tend to focus on aesthetic requirements and are often used in green development. Since the aesthetic requirements and pressure requirements, as well as green roofs thermal insulation function, reduce the heat island effect, silencer effect, extend the life of the roof.Green roofs in Germany, the most widely used, followed in North America, but to consider the impact on the aesthetics. Germany is by far the most experienced countries in the 19th century have practical application, then as an alternative to reduce the risk of fire tar roof an option in urban areas. Germany is currently the main research question on the cultivation of other issues to consider smaller cities. A study from 1987 to 1989, was found packed with 70 mm thick green roof can be reduced by 60% -80% of heat loss. In a Canadian work computer model based on the roof indicates that as long as the sump, the area can reach 70% of the roof area can be reduced by 60 percent in one year, the same model was also used for artificial rainfall, which the results indicate that rainfall in the catchment season helps to drain away rainwater.However, none of these studies show that green roofs can play a useful role in the rainfall season, or how high collection efficiency of water supply. The United States did some tests, as long as the green roofs regular watering, can reduce 65 percent of the runoff in a rainfall. America's most authoritative green roof guidelines by the New Jersey state environmental agencies promulgated. The mainprinciple is to solve the structural problems of light, and how can the normal drainage after two years.Rainfall period is based on the probability of failure is determined. The system is typically based on rainfall during rainstorms two minutes, two minutes, have a choice. Although this model will get more traffic, but there is no other better alternative. Studies have shown that the traditional model is applied to study green roofs are premature.Loss factor than traditional roof records should be small, about 98.7%. Peak flow will be reduced, although not penetrate, the surface roughness but also have a significant impact.Concentrated rainfall than two minutes for a long time, especially for large roof areas, such as public buildings, commercial buildings, industrial buildings.Urban drainage design should also consider other factors, for a complex system, a green roof in a rain is not enough. Water flow duration curve shows a longer than traditional systems. And two independent and will affect between is possible, which requires a more precise time period.3. Rainwater CollectorBasic requirements rainwater collector is designed to be able to accommodate rainfall rainstorms. Although it is possible to make a slightly inclined roof drainage purposes, but the nature of the construction industry and building settlement will become flat roof Typically, the tank is placed in a horizontal, sectional view of the water is outwardly inclined, which the role of hydrostatic.3.1 drain outletAnalyzing rainwater collector has sufficient volume is the key to the sump outlet external setting conditions. Also affect the flow rate into the storm water drainage system piping, but also affect the depth of the water catchment. Although the depth of the sump will not bring any particular problems, but too deep can cause excessive sump.Numerous studies in the 1980s showed that the flow of conventional roof drainage system outlet can be divided into two cases. It depends on the size of the depth and size of the outlet. When the water depth is less than half the diameter of the outlet, the flow of the first type, and the outlet of the flow can be calculated by an appropriate equation; water depth increases, exports are slowly clogging the flow will become another form forms, at the same time, the flow of exports can be obtained through other equations. While conventional roof drainage systems are designed to be free-draining, but may cause limitations encountered in the design of the flow is not free. In this case, it will require additional depth.Siphon roof drainage systems, the outlet is designed to be submerged stream. In this case, the depth of the outlet of the decision is more complicated, because the design of the sump depends on the flow. Recent studies have shown that conventional roof drainage systems use a variety of non-standard catchment, their depth and height, bigger than the diameter of the outlet. This will eventually result in a siphon effect. For a given catchment, the flow depends on the starting end of the drop tube diameter. A similar phenomenon has also been used to study the standardcatchment, in these circumstances, only limited siphon action occurs within relatively close distance from the exit.3.2 tank flow classificationIn the complex flow sump outlet flow classification, can be seen from Table 2a, the flow will be uniform layering, regardless of whether the same inlet flow. Table 2b and 2c show, export distribution will greatly influence the flow.When the outlet is not a free jet, sump outlet complex flow classification is difficult to describe. Because each catchment tank pressures are likely to be merged. For example, the siphon tube system design point is at near full jet outlet flow classification depends on the energy loss of each branch.3.3 hydrostatic sectionalSump shape of the water surface in the canal can be classified according to the flow equation. In most cases, a low flow rate means that there is less friction loss, if exports are free jet, the friction loss is negligible cross-section through the hydrostatic equation 1 to determine the horizontal distance.Where Q-- flow (m3 / s)T- surface width (m)g- acceleration of gravity (m / s2)F- flow area (m2)Equation 1 can not be ignored when the friction required to correct (or very long pipe velocity is large), or not a free jet.3.4 The current design methodsThe previous discussion has highlighted the main factors that should be considered with sink design. However, without the help of a certain number of models, computing hydrostatic sectional roof drainage system, the volume of the sump is possible. This large commercial and manufacturing industry, is a development opportunity, you can merge several kilometers of water routes. Thus, the conventional drainage system sump design methods are mainly based on experience, and assume that exports are free jet.Sump location in the building, it may cause the example to fail.Different interface sumpExcept in the case cited above, but also allows designers to use empirical data.3.5 Digital ModelLarge number of digital models can be used to accurately describe the flow of any form of catchment tank, regardless of whether the roof flows stable. An example of this model is a combination of roof space model. This model enables users to classify different aspects of the data indicated, includes: details of the rains, the roof surface drainage and other details. Kinematics have also been used to study rainwater tank to flow from the research collection. A typical method is based on open system to solve a basic problem of spatial mobility. This model automatically resolve the sump outlet flow situation, but also to deal with the case of free jet can also be simulated space limited mobility and submerged discharge. Output values include depth and flow rate.Currently, the model is essentially just a variety of research tools, but alsothrough practical engineering test. However, we should face up to the various role models.4 pipe systems groupComposition in the form and scope of the tube group determines the roof drainage system relies mainly on the traditional system or siphon action.4.1 Traditional stormwater systemsConventional roof drainage systems, the ground plane is generally vertical pipe-line network, connected to the sump outlet and underground drainage systems, critical systems as well as compensating tube. It should be emphasized that the angle bet ween the ground and the compensating tube is less than 10 °. Capacity of the entire system relies mainly on the outlet tube instead of down.Flow vertical tube is usually free-flowing, full of only 33%, the efficiency depends on the excess length of the tube. If the drop tube long enough (typically greater than 5m), there may be an annular flow. Similarly, under normal circumstances flow compensation pipe is free-flowing, full of up to 70%. Such designed process both for the design, various equations can also be used.4.2 Siphon roof drainage systemIn contrast with the traditional drainage systems, Siphon roof drainage system relies on air flow outside the system, and the tube is full pipe flow stream.The designs are usually made on the assumption that the design of heavy rain, the system can quickly siphon discharge rainwater. This assumption allows the application of hydrostatic siphon system theory. Often used steady flow energy equation. While this approach ignores the small amount of energy loss at the entrance, but after the experiment showed that there are still conducive to practical use.However, steady-state design methods in the siphon system is exposed to rain when the system does not meet the standard requirements or changes in rainfall intensity is large is not applied. In the first case, there will be some mixing of air quality, annular flow occurs. These problems are not integrated in the system when more serious. Because usually designed rains are common, it is clear now design methodology over time may not apply to siphon system. This is a major disadvantage, because the design of the main problem is the noise and vibration problems.Despite the disadvantages of the prior design approach, but a lot of the world's very few engineering failure reports. When a failure occurs, most likely for the following reasons:An incorrect understanding of the operation pointsSubstandard materials listInstallation defectsMaintenance mismanagementTo overcome these disadvantages, we have recently launched a series of research projects, to discuss the siphon system, and the development of digital models. From this work we learn a lot.In contrast with conventional design methods of some assumptions, siphon system mainly has the following aspects:1) non-flow system of full flow2) levels of certain pipe-flowing full pipe flow3) full pipe flow downstream propagation through a vertical pipe, riser, etc.4) the inner tube flow occurs over the vertical section, the system to reduce the pressure5) downward tube is full pipe flow, there will be air lock6) appears completely siphon action until well into the air system is lower thana certain levelTable 4a column data indicate that below the design point, the system will siphon unstable flow, depth of the water collecting tank is insufficient to maintain the siphon action. Table 4b show that the unsteady flow in siphon system when it will appear.Table 5 lists the data output of a digital model. It can be seen that the model can accurately describe the siphon action, siphon and steady state, the data also show that the model can accurately describe the complex siphon action.5 ConclusionThis article has illustrated the critical roof drainage systems, but these are often overlooked in the urban drainage system design. This article also shows that the design process is a complex process, rely mainly on the performance of exports. The following conclusions are based on the design summed up:1) Run depend on three interacting parts: the roof, sump, water pipes2) Green roofs can reduce traffic and beautify the city3) the export performance of the system is essential4) siphon drainage system have a greater advantage in large-scale projects, but must be considered high maintenance costs5) Design siphon drainage system should consider additional capacity and operational issuesAlthough the green roof is a more attractive option, but the traditional roof of a building in the country will continue to dominate. Green roofs will be gradually developed, and gradually been widely accepted. Similarly, the roof drainage system shown effective that it will continue to play a huge role in the commercial building drainage systems.Roof drainage system of the greatest threats from climate change, existing systems tend to be not simply aging; rainfall patterns of change will result in inefficient operation, self-cleaning rate will be reduced. Changes in wind speed and the roof will also accelerate the aging of the roof, it is necessary to carry out maintenance. Taking into account the climate change, the increase in materials, roof collected rainwater will be more extensive. Currently, the amount of rain around the globe per person per day 7-300 liters in the UK, with an average consumption of 145L / h / d, of which only about one liter is used by people, about 30 per cent of the toilet, study shows If water shortage, rainwater collected on the roof of developed and developing countries are recommended approach.屋顶排水设计性能的近期与远期优势最近十年见证了屋顶排水系统设计方面的巨大变化，特别的是，虹吸雨水排水系统已经得到逐步改善，并且有可能得到重点应用。
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本科毕业设计外文文献及译文文献、资料题目：Sealed building drainageand vent systems文献、资料来源：国道数据库文献、资料发表（出版）日期：2005.9.12院（部）：市政与环境工程学院专业：给水排水工程班级：姓名：学号：指导教师：翻译日期： 2012.06外文文献：Sealed building drainage and vent systems—an application of active air pressure transient control and suppression AbstractThe introduction of sealed building drainage and vent systems is considered a viable proposition for complex buildings due to the use of active pressure transient control and suppression in the form of air admittance valves and positive air pressure attenuators coupled with the interconnection of the network's vertical stacks.This paper presents a simulation based on a four-stack network that illustrates flow mechanisms within the pipework following both appliance discharge generated, and sewer imposed, transients. This simulation identifies the role of the active air pressure control devices in maintaining system pressures at levels that do not deplete trap seals.Further simulation exercises would be necessary to provide proof of concept, and it would be advantageous to parallel these with laboratory, and possibly site, trials for validation purposes. Despite this caution the initial results are highly encouraging and are sufficient to confirm the potential to provide definite benefits in terms of enhanced system security as well as increased reliability and reduced installation and material costs.Keywords: Active control; Trap retention; Transient propagationNomenclatureC+-——characteristic equationsc——wave speed, m/sD——branch or stack diameter, mf——friction factor, UK definition via Darcy Δh=4fLu2/2Dgg——acceleration due to gravity, m/s2K——loss coefficientL——pipe length, mp——air pressure, N/m2t——time, su——mean air velocity, m/sx——distance, mγ——ratio specific heatsΔh——head loss, mΔp——pressure difference, N/m2Δt——time step, sΔx——internodal length, mρ——density, kg/m3Article OutlineNomenclature1. Introduction—air pressure transient control and suppression2. Mathematical basis for the simulation of transient propagation in multi-stack building drainage networks3. Role of diversity in system operation4. Simulation of the operation of a multi-stack sealed building drainage and vent system5. Simulation sign conventions6. Water discharge to the network7. Surcharge at base of stack 18. Sewer imposed transients9. Trap seal oscillation and retention10. Conclusion—viability of a sealed building drainage and vent system1.Air pressure transients generated within building drainage and vent systems as a natural consequence of system operation may be responsible for trap seal depletion and cross contamination of habitable space [1]. Traditional modes of trap seal protection, based on the Victorian engineer's obsession with odour exclusion [2], [3] and [4], depend predominantly on passive solutions where reliance is placed on cross connections and vertical stacks vented to atmosphere [5] and [6]. This approach, while both proven and traditional, has inherent weaknesses, including the remoteness of the vent terminations [7], leading to delays in the arrival of relieving reflections, and the multiplicity of open roof level stack terminations inherent within complex buildings. The complexity of the vent system required also has significant cost and space implications [8].The development of air admittance valves (AAVs) over the past two decades provides the designer with a means of alleviating negative transients generated as random appliance discharges contribute to the time dependent water-flow conditions within the system. AAVs represent an active control solution as they respond directly to the local pressure conditions, opening as pressurefalls to allow a relief air inflow and hence limit the pressure excursions experienced by the appliance trap seal [9].However, AAVs do not address the problems of positive air pressure transient propagation within building drainage and vent systems as a result of intermittent closure of the free airpath through the network or the arrival of positive transients generated remotely within the sewer system, possibly by some surcharge event downstream—including heavy rainfall in combined sewer applications.The development of variable volume containment attenuators [10] that are designed to absorb airflow driven by positive air pressure transients completes the necessary device provision to allow active air pressure transient control and suppression to be introduced into the design of building drainage and vent systems, for both ‘standard’ buildings and those requiring particular attention to be paid to the security implications of multiple roof level open stack terminations. The positive air pressure attenuator (PAPA) consists of a variable volume bag that expands under the influence of a positive transient and therefore allows system airflows to attenuate gradually, therefore reducing the level of positive transients generated. Together with the use of AAVs the introduction of the PAPA device allows consideration of a fully sealed building drainage and vent system.Fig. 1 illustrates both AA V and PAPA devices, note that the waterless sheath trap acts as an AA V under negative line pressure.Fig. 1. Active air pressure transient suppression devices to control both positive and negative surges.Active air pressure transient suppression and control therefore allows for localized intervention to protect trap seals from both positive and negative pressure excursions. This hasdistinct advantages over the traditional passive approach. The time delay inherent in awaiting the return of a relieving reflection from a vent open to atmosphere is removed and the effect of the transient on all the other system traps passed during its propagation is avoided.2.Mathematical basis for the simulation of transient propagation in multi-stack building drainage networks.The propagation of air pressure transients within building drainage and vent systems belongs to a well understood family of unsteady flow conditions defined by the St Venant equations of continuity and momentum, and solvable via a finite difference scheme utilizing the method of characteristics technique. Air pressure transient generation and propagation within the system as a result of air entrainment by the falling annular water in the system vertical stacks and the reflection and transmission of these transients at the system boundaries, including open terminations, connections to the sewer, appliance trap seals and both AAV and PAPA active control devices, may be simulated with proven accuracy. The simulation [11] provides local air pressure, velocity and wave speed information throughout a network at time and distance intervals as short as 0.001 s and 300 mm. In addition, the simulation replicates local appliance trap seal oscillations and the operation of active control devices, thereby yielding data on network airflows and identifying system failures and consequences. While the simulation has been extensively validated [10], its use to independently confirm the mechanism of SARS virus spread within the Amoy Gardens outbreak in 2003 has provided further confidence in its predictions [12].Air pressure transient propagation depends upon the rate of change of the system conditions. Increasing annular downflow generates an enhanced entrained airflow and lowers the system pressure. Retarding the entrained airflow generates positive transients. External events may also propagate both positive and negative transients into the network.The annular water flow in the ‘wet’ stack entrains an airflow due to the condition of ‘no slip’ established between the annular water and air core surfaces and generates the expected pressure variation down a vertical stack. Pressure falls from atmospheric above the stack entry due to friction and the effects of drawing air through the water curtains formed at discharging branch junctions. In the lower wet stack the pressure recovers to above atmospheric due to the traction forces exerted on the airflow prior to falling across the water curtain at the stack base.The application of the method of characteristics to the modelling of unsteady flows was first recognized in the 1960s [13]. The relationships defined by Jack [14] allows the simulation to model the traction force exerted on the entrained air. Extensive experimental data allowed the definition of a ‘pseudo-friction factor’ applicable in the wet stack and operable across the water annular flow/entrained air core interface to allow combined discharge flows and their effect on airentrainment to be modelled.The propagation of air pressure transients in building drainage and vent systems is defined by the St Venant equations of continuity and momentum [9],(1)(2)These quasi-linear hyperbolic partial differential equations are amenable to finite difference solution once transformed via the Method of Characteristics into finite difference relationships, Eqs. (3)–(6), that link conditions at a node one time step in the future to current conditions at adjacent upstream and downstream nodes, Fig. 2.Fig.2. St Venant equations of continuity and momentum allow airflow velocity and wave speed to bepredicted on an x-t grid as shown. Note , .For the C+ characteristic:(3)when(4)and the C- characteristic:(5)when(6)where the wave speed c is given byc=(γp/ρ)0.5. (7) These equations involve the air mean flow velocity, u, and the local wave speed, c, due to the interdependence of air pressure and density. Local pressure is calculated as(8)Suitable equations link local pressure to airflow or to the interface oscillation of trap seals.The case of the appliance trap seal is of particular importance. The trap seal water column oscillates under the action of the applied pressure differential between the transients in the network and the room air pressure. The equation of motion for the U-bend trap seal water column may be written at any time as(9)It should be recognized that while the water column may rise on the appliance side, conversely on the system side it can never exceed a datum level drawn at the branch connection.In practical terms trap seals are set at 75 or 50 mm in the UK and other international standards dependent upon appliance type. Trap seal retention is therefore defined as a depth less than the initial value. Many standards, recognizing the transient nature of trap seal depletion and the opportunity that exists for re-charge on appliance discharge allow 25% depletion.The boundary equation may also be determined by local conditions: the AAV opening and subsequent loss coefficient depends on the local line pressure prediction.Empirical data identifies the AAV opening pressure, its loss coefficient during opening and at the fully open condition. Appliance trap seal oscillation is treated as a boundary condition dependent on local pressure. Deflection of the trap seal to allow an airpath to,or from, the appliance or displacement leading to oscillation alone may both be modelled. Reductions in trap seal water mass during the transient interaction must also be included.3. Role of diversity in system operationIn complex building drainage networks the operation of the system appliances to discharge water to the network, and hence provide the conditions necessary for air entrainment and pressure transient propagation, is entirely random. No two systems will be identical in terms of their usage at any time. This diversity of operation implies that inter-stack venting paths will be established if the individual stacks within a complex building network are themselves interconnected. It is proposed that this diversity is utilized to provide venting and to allow serious consideration to be given to sealed drainage systems.In order to fully implement a sealed building drainage and vent system it would be necessary for the negative transients to be alleviated by drawing air into the network from a secure space andnot from the external atmosphere. This may be achieved by the use of air admittance valves or at a predetermined location within the building, for example an accessible loft space.Similarly, it would be necessary to attenuate positive air pressure transients by means of PAPA devices. Initially it might be considered that this would be problematic as positive pressure could build within the PAPA installations and therefore negate their ability to absorb transient airflows. This may again be avoided by linking the vertical stacks in a complex building and utilizing the diversity of use inherent in building drainage systems as this will ensure that PAPA pressures are themselves alleviated by allowing trapped air to vent through the interconnected stacks to the sewer network.Diversity also protects the proposed sealed system from sewer driven overpressure and positive transients. A complex building will be interconnected to the main sewer network via a number of connecting smaller bore drains. Adverse pressure conditions will be distributed and the network interconnection will continue to provide venting routes.These concepts will be demonstrated by a multi-stack network.4. Simulation of the operation of a multi-stack sealed building drainage and vent systemFig. 3 illustrates a four-stack network. The four stacks are linked at high level by a manifold leading to a PAPA and AAV installation. Water downflows in any stack generate negative transients that deflate the PAPA and open the AAV to provide an airflow into the network and out to the sewer system. Positive pressure generated by either stack surcharge or sewer transients are attenuated by the PAPA and by the diversity of use that allows one stack-to-sewer route to act as a relief route for the other stacks.The network illustrated has an overall height of 12m. Pressure transients generated within thenetwork will propagate at the acoustic velocity in air . This implies pipe periods, from stack base to PAPA of approximately 0.08s and from stack base to stack base of approximately 0.15s.In order to simplify the output from the simulation no local trap seal protection is included—for example the traps could be fitted with either or both an AAV and PAPA as examples of active control. Traditional networks would of course include passive venting where separate vent stacks would be provided to atmosphere, however a sealed building would dispense with this venting arrangement.Fig.3.Four stack building drainage and vent system to demonstrate the viability of a sealed building system.Ideally the four sewer connections shown should be to separate collection drains so that diversity in the sewer network also acts to aid system self venting. In a complex building this requirement would not be arduous and would in all probability be the norm. It is envisagedthat the stack connections to the sewer network would be distributed and would be to a below ground drainage network that increased in diameter downstream. Other connections to the network would in all probability be from buildings that included the more traditional open vent system design so that a further level of diversity is added to offset any downstream sewer surcharge events of long duration. Similar considerations led to the current design guidance for dwellings.It is stressed that the network illustrated is representative of complex building drainage networks. The simulation will allow a range of appliance discharge and sewer imposed transient conditions to be investigated.The following appliance discharges and imposed sewer transients are considered:1. w.c. discharge to stacks 1–3 over a period 1–6s and a separate w.c. discharge to stack 4 between 2 and 7s.2. A minimum water flow in each stack continues throughout the simulation, set at 0.1L/s, to represent trailing water following earlier multiple appliance discharges.3. A 1s duration stack base surcharge event is assumed to occur in stack 1 at 2.5s.4. Sequential sewer transients imposed at the base of each stack in turn for 1.5s from 12 to 18s.The simulation will demonstrate the efficacy of both the concept of active surge control and inter-stack venting in enabling the system to be sealed, i.e. to have no high level roof penetrations and no vent stacks open to atmosphere outside the building envelope.The imposed water flows within the network are based on ‘real’ system values, being representative of current w.c. discharge characteristics in terms of peak flow, 2l/s, overall volume, 6l, and duration, 6s. The sewer transients at 30mm water gauge are representative but not excessive. Table 1 defines the w.c. discharge and sewer pressure profiles assumed.Table1. w.c. discharge and imposed sewer pressure characteristicsw.c. discharge characteristic Imposed sewer transient at stack baseTime Discharge flow Time PressureSeconds l/s Seconds Water gauge (mm)Start time 0.0 Start time 0.0+2 2.0 +0.5 30.0+4 2.0 +0.5 30.0+6 0.0 +0.5 0.05. Simulation conventionsIt should be noted that heights for the system stacks are measured positive upwards from the stack base in each case. This implies that entrained airflow towards the stack base is negative. Airflow entering the network from any AAVs installed will therefore be indicated as negative. Airflow exiting the network to the sewer connection will be negative.Airflow entering the network from the sewer connection or induced to flow up any stack will be positive.Water downflow in a vertical is however regarded as positive.Observing these conventions will allow the following simulation to be better understood.6. Water discharge to the networkTable 1 illustrates the w.c. discharges described above, simultaneous from 1s to stacks 1–3 and from 2s to stack 4. A base of stack surcharge is assumed in stack 1 from 2.5 to 3s. As a result it will be seen from Fig. 4 that entrained air downflows are established in pipes 1, 6 and 14 asexpected. However, the entrained airflow in pipe 19 is into the network from the sewer. Initially, as there is only a trickle water flow in pipe 19, the entrained airflow in pipe 19 due to the w.c. discharges already being carried by pipes 1, 6 and 14, is reversed, i.e. up the stack, and contributes to the entrained airflow demand in pipes 1, 6 and 14. The AAV on pipe 12 also contributes but initially this is a small proportion of the required airflow and the AAV flutters in response to local pressure conditions.Fig.4.Entrained airflows during appliance discharge.Following the w.c. discharge to stack 4 that establishes a water downflow in pipe 19 from 2 s onwards, the reversed airflow initially established diminishes due to the traction applied by the falling water film in that pipe. However, the suction pressures developed in the other three stacks still results in a continuing but reduced reversed airflow in pipe 19. As the water downflow in pipe 19 reaches its maximum value from 3 s onwards, the AAV on pipe 12 opens fully and an increased airflow from this source may be identified. The flutter stage is replaced by a fully open period from 3.5 to 5.5 s.Fig. 5 illustrates the air pressure profile from the stack base in both stacks 1 and 4 at 2.5 s into the simulation. The air pressure in stack 4 demonstrates a pressure gradient compatible with the reversed airflow mentioned above. The air pressure profile in stack 1 is typical for a stack carrying an annular water downflow and demonstrates the establishment of a positive backpressure due to the water curtain at the base of the stack.Fig.5.Air pressure profile in stacks 1 and 4 illustrating the pressure gradient driving the reversed airflow in pipe 19.The initial collapsed volume of the PAPA installed on pipe 13 was 0.4l, with a fully expanded volume of 40l, however due to its small initial volume it may be regarded as collapsed during this phase of the simulation.7. Surcharge at base of stack 1Fig. 6 indicates a surcharge at the base of stack 1, pipe 1 from 2.5 to 3 s. The entrained airflow in pipe 1 reduces to zero at the stack base and a pressure transient is generated within that stack, Fig.6. The impact of this transient will also be seen later in a discussion of the trap seal responses for the network.Fig.6.Air pressure levels within the network during the w.c. discharge phase of the simulation. Note surcharge at base stack 1, pipe 1 at 2.5s.It will also be seen, Fig. 6, that the predicted pressure at the base of pipes 1, 6 and 14, in the absence of surcharge, conform to that normally expected, namely a small positive back pressure as the entrained air is forced through the water curtain at the base of the stack and into the sewer. In the case of stack 4, pipe 19, the reversed airflow drawn into the stack demonstrates a pressure drop as it traverses the water curtain present at that stack base.The simulation allows the air pressure profiles up stack 1 to be modelled during,and following, the surcharge illustrated in Fig. 6. Fig. 7(a) and (b) illustrate the air pressure profiles in the stack from 2.0 to 3.0 s, the increasing and decreasing phases of the transient propagation being presented sequentially. The traces illustrate the propagation of the positive transient up the stack as well as the pressure oscillations derived from the reflection of the transient at the stack termination at the AAV/PAPA junction at the upper end of pipe 11.Fig.7.(a) Sequential air pressure profiles in stack 1 during initial phase of stack base surcharge. (b) Sequential air pressure profiles in stack 1 during final phase of stack base surcharge.8. Sewer imposed transientsTable 2 illustrates the imposition of a series of sequential sewer transients at the base of eachstack. Fig. 8 demonstrates a pattern that indicates the operation of both the PAPA installed on pipe 13 and the self-venting provided by stack interconnection.Fig.8.Entraind airflows as a result of sewer imposed pressure transients.As the positive pressure is imposed at the base of pipe 1 at 12 s, airflow is driven up stack 1 towards the PAPA connection. However, as the base of the other stacks have not a yet had positive sewer pressure levels imposed, a secondary airflow path is established downwards to the sewer connection in each of stacks 2–4, as shown by the negative airflows in Fig. 8.As the imposed transient abates so the reversed flow reduces and the PAPA discharges air to the network, again demonstrated by the simulation, Fig. 8. This pattern repeats as each of the stacks is subjected to a sewer transient.Fig. 9 illustrates typical air pressure profiles in stacks 1 and 2. The pressure gradient in stack 2 confirms the airflow direction up the stack towards the AAV/PAPA junction. It will be seen that pressure continues to decrease down stack 1 until it recovers, pipes 1 and 3, due to the effect of the continuing waterflow in those pipes.The PAPA installation reacts to the sewer transients by absorbing airflow, Fig. 10. The PAPA will expand until the accumulated air inflow reaches its assumed 40 l volume. At that point the PAPA will pressurize and will assist the airflow out of the network via the stacks unaffected by the imposed positive sewer transient. Note that as the sewer transient is applied sequentially from stacks 1–4 this pattern is repeated. The volume of the high level PAPA, together with any others introduced into a more complex network, could be adapted to ensure that no system pressurization occurred.Fig.9.Air pressure profile in stack 1 and 2 during the sewer imposed transient in stack 2, 15s into the simulation.Fig.10.PAPA volume and AAV throughflow during simulation.The effect of sequential transients at each of the stacks is identifiable as the PAPA volume decreases between transients due to the entrained airflow maintained by the residual water flows in each stack.9. Trap seal oscillation and retentionThe appliance traps connected to the network monitor and respond to the local branch air pressures. The model provides a simulation of trap seal deflection, as well as final retention. Fig. 11(a,b) present the trap seal oscillations for one trap on each of the stacks 1 and 2, respectively. As the air pressure falls in the network, the water column in the trap is displaced so that the appliance side water level falls. However, the system side level is governed by the level of the branch entry connection so that water is lost to the network. This effect is illustrated in both Fig. 11(a) and (b).Transient conditions in the network result in trap seal oscillation, however at the end of the event the trap seal will have lost water that can only be replenished by the next appliance usage. If the transient effects are severe than the trap may become totally depleted allowing a potential cross contamination route from the network to habitable space. Fig. 11(a) and (b) illustrate the trap seal retention at the end of the imposed network transients.Fig.11.(a) Trap seal oscillation, trap 2. (b) Trap seal oscillation, trap 7.Fig. 11(a), representing the trap on pipe 2, illustrates the expected induced siphonage of trap seal water into the network as the stack pressure falls. The surcharge event in stack 1 interrupts this process at 2s. The trap oscillations abate following the cessation of water downflow in stack 1. The imposition of a sewer transient is apparent at 12s by the water surface level rising in the appliance side of the trap. A more severe transient could have resulted in ‘bubbling through’ at this stage if the trap system side water surface level fell to the lowest point of the U-bend.The trap seal oscillations for traps on pipes 7, Fig. 11(b) and 15, are identical to each other until the sequential imposition of sewer transients at 14 and 16s. Note that thesurcharge in pipe 1 does not affect these traps as they are remote from the base of stack 1. The trap on pipe 20 displays an initial reduction in pressure due to the delay in applied water downflow. The sewer transient in pipe 19 affects this trap at around 18s.As a result of the pressure transients arriving at each trap during the simulation there will be a loss of trap seal water. This overall effect results in each trap displaying an individual water seal retention that depends entirely on the usage of the network. Trap 2 retains 32mm water seal while traps 7 and 15 retain 33mm. Trap 20 is reduced to 26mm water seal. Note that the traps on pipes 7 and 15 were exposed to the same levels of transient pressure despite the time difference in arrival of the sewer transients. Fig. 11(a) and (b) illustrate the oscillations of the trap seal column as a result of the solution of the trap seal boundary condition, Eq. (10), with the appropriate C+ characteristic. This boundary condition solution continually monitors the water loss from the trap and at the end of the event yields a trap seal retention value. In the example illustrated the initial trap seal values were taken as 50mm of water, common for appliances such as w.c.'s and sinks.10. Conclusion—viability of a sealed building drainage and vent systemThe simulation presented confirms that a sealed building drainage system utilizing active transient control would be a viable design option. A sealed building drainage system would offer the following advantages:• System security would be immeasurably enhanced as all high-level open system terminations would be redundant.• System complexity would be reduced while system predictability would increase.• Space and material savings would be achieved within the construction phase of any installation.These benefits would be realized provided that active transient control and suppression was incorporated into the design in the form of both AAV to suppress negative transients and variable volume containment devices (PAPA) to control positive transients.The diversity inherent in the operation of both building drainage and vent systems and the sewers connected to the building have a role in providing interconnected relief paths as part of the system solution.The method of characteristics based finite difference simulation presented has provided output consistent with expectations for the operation of the sealed system studied. The accuracy of the simulation in other recent applications, including the accurate corroboration of the SARS spread mechanism within the Amoy Gardens complex in Hong Kong in 2003, provides a confidence level in the results presented.。