Development of compact heat exchangers for CO2 air-conditioning systems
316L不锈钢扩散焊接头高温蠕变性能
316L不锈钢扩散焊接头高温蠕变性能安子良;轩福贞;涂善东【摘要】以非标准持久试样进行了316L不锈钢扩散焊接头蠕变与持久试验.采用θ函数法描述和预测了316L不锈钢扩散焊接头蠕变曲线,并由θ函数法计算了最小蠕变应变速率和接头在6MPa,550℃条件下蠕变应变达到0.2％时的使用寿命,并将蠕变应变0.2％作为以316L不锈钢为母材的扩散焊构件高温结构设计标准.由持久试验结果可知,θ函数法与Larson - Miller法外推的316L不锈钢直接扩散焊接头蠕变断裂时间较为一致.%The non - standard specimen is used in the creep and stress rupture test of the 316L stainless steel direct diffusion bonding joint. The creep curve is interpreted in terms of the 6 project concept method , the minimum creep strain rate, creep curve and remain life at 6 Mpa are calculated by using 0 project method,the creep strain of 0.2% is select as the design criterion for the diffusion bonding component at high temperature. As known form the stress rupture experimental results, the remaining life extrapolated by Larsen - Miller equation is relatively consistent with that calculated by the 8 project concept method.【期刊名称】《压力容器》【年(卷),期】2011(028)007【总页数】5页(P6-10)【关键词】扩散焊;蠕变变形;持久强度;θ函数法【作者】安子良;轩福贞;涂善东【作者单位】上海应用技术学院机械工程学院,上海201418;华东理工大学机械与动力工程学院,上海200237;华东理工大学机械与动力工程学院,上海200237【正文语种】中文【中图分类】TG453.9;TG142.70 引言扩散焊技术以其加工精度高、适于复杂几何结构加工的特点，成为先进制造技术领域和微小型化学机械系统封装的首选加工工艺，非常适合制备工作高温高压环境中的微小型换热器、反应器和微槽道反应器等［1－4］。
A-07010-CO2循环系统中回热器作用分析
式中，pop代表最优高压侧压力，单位bar；TGC代表气体冷却器出口温度，单位℃。
Δε / ε / %
10
9
制冷
8
制热
7
T0＝－5℃
T ＝－10℃ 0
T ＝－15℃ 0
6
5
4
T ＝－5℃
0
3
T0＝－10℃
2
T0＝－15℃
1
0 30 35 40 45 50 55 60 65 70 75 80
t/℃
图 5 过热 5℃时不同蒸发温度下系统性能随冷凝温度的变化 图 5 和图 6 分别列出了压缩机吸气过热度 5℃和 10℃情况下，不同蒸发温度时系统 性能改变随冷凝温度的变化曲线。通过比较可以看到，制冷性能的改善随着蒸发温度和 冷凝温度的升高而升高；制热性能的改善随着蒸发温度的升高而略有升高，随着冷凝温 度的升高基本保持不变。压缩机吸气过热度为 5℃时，制冷系数和单位容积制冷量的改 善小于 10％；制热系数和单位容积制热量的改善小于 3％。压缩机吸气过热度为 10℃时， 制热系数和单位容积制热量的改善小于 6％；当气体冷却器出口温度小于 40℃时，制冷 系数和单位容积制冷量的改善小于 10％；当气体冷却器出口温度介于 40℃和 70℃之间 时，制冷系数和单位容积制冷量的改善介于 10％和 20％之间。随着冷凝温度的升高， 制冷性能的改善明显优于制热性能的改善。
当CO2气体冷却器出口温度高于其临界温度时，气体冷却器内的CO2不再处于两相状 态，而是处于超临界状态，此时CO2的温度和压力可以独立变化，并且不同的气体冷却 器出口温度对应一个最优的高压侧压力。本文采用文献[11]确定的最优高压侧压力作为 计算冷凝压力：
pop = 2.56TGC − 4.2
基于ZigBee的工业现场数字温度无线采集系统设计
基于ZigBee的工业现场数字温度无线采集系统设计钱丹浩;刘萍萍【期刊名称】《化工自动化及仪表》【年(卷),期】2011(038)009【摘要】在详细分析无线数据采集工作原理的基础上,进行了基于ZigBee的工业现场数字温度的无线采集设计,给出了其硬件设计方案并论述其工作过程,设计了程序的主要工作流程和算法.%According to requirements of wind tunnel test, a performance test system for compact heat exchangers was presented. The system has the function of test, data acquisition, data storage and analysis, and takes LabVIEW as the developer tool to have virtual instrument and testing technology combined.【总页数】4页(P1119-1121,1124)【作者】钱丹浩;刘萍萍【作者单位】南京化工职业技术学院,南京210048;南京化工职业技术学院,南京210048【正文语种】中文【中图分类】TP274【相关文献】1.基于ZigBee的无线温度采集系统设计 [J], 李宝山;赵飞龙2.基于ZigBee技术和DS18B20的无线温度采集系统设计 [J], 岳瑶;张瑜;3.基于Zigbee的多路温度数据无线采集系统设计 [J], 丁凡;周永明4.基于ARM和ZigBee的无线温度采集系统设计 [J], 崔京伟;黄灏5.基于ZigBee的无线温度采集系统设计 [J], 沈慧钧因版权原因，仅展示原文概要，查看原文内容请购买。
板式热交换器介绍(英文版)
Plate Heat Exchanger - evolution
1931 2001
• • • • •
5-10 mm thick plate Milled pattern Liquids passed the plate horizontally several times Stainless steel Up to 5 m2 per unit
• • • • • • •
Steel and metal works Power and energy production Chemical process industries Petroleum industries Refrigeration Engineering industries Central cooling engineering
Main heat transfer area
Thin sheet design, cold formed in single step hydraulic pressing (up to 40000 tons)
Plate pack - example single pass
End Plate II Channel plates End Plate I
Semiwelded PHE range
AlfaCond in reality
Why AlfaCond?
…instead of shell-and-tube
• • • • •
Save money Save space Easier maintenance Easy to increase capacity Counter-current flow
Plate Heat Exchangers
不同翅片形式管翅式换热器流动换热性能比较
不同翅片形式管翅式换热器流动换热性能比较摘要：随着制冷空调行业的发展,人们已经把注意力集中在高效、节能节材的紧凑式换热器的开发上,而翅片管式换热器正是制冷、空调领域中所广泛采用的一种换热器形式。
对于它的研究不仅有利于提高换热器的换热效率及其整体性能,而且对改进翅片换热器的设计型式,推出更加节能、节材的紧凑式换热器有着重要的指导意义。
由于翅片管式换热器在翅片结构形式和几何尺寸的不同,造成其换热性能和阻力性能上的极大差异。
本文概述目前国内外空调制冷行业中的普遍采用的几种不同翅片类型（平直翅片、波纹翅片、开缝翅片、百叶窗形翅片）的换热及压降实验关联式及其影响因素，对不同翅片形式的管翅式换热器的换热及压降特性的实验关联式进行总结，并对不同翅片的流动换热性能进行了比较。
正确地选用实验关联式及性能指标，将对翅片管式换热器的优化设计及其制造提供可靠的依据。
关键词：翅片形式；管翅式；换热器；关联式；流动换热性能Study on heat transfer and flow characteristics of fin-and-tube heat exchangers with various fintypesAbstract：With the development of refrigeration and air conditioning, high efficiency, energy saving and material saving compact type of heat exchanger is development, as one kind of compact heat exchanger, fin-and-tube heat exchanger has a wide application in future. It is necessary to develop compact heat exchanger which is more energy saving and material saving to improve the heat exchanger thermal efficiency and the overall performance of heat transfer.This paper summaries the heat transfer and pressure drop correlations of different fin surfaces, and the corresponding influencing factors. The heat transfer and friction characteristic of these kinds of fin types are compared, and the results show the difference of these fin types. The appropriate correlation and evaluation criterion will provide reliable foundation to the design and optimization of compact heat exchangers.Key words：Fin-and-tube heat exchanger; Heat transfer and flow characteristics; Experimental correlations; Comparison目录1 绪论 (2)1.1课题背景及研究意义 (3)1.2管翅式换热器简介 (3)1.3管翅式换热器的特点 (4)1.4 管翅式换热器的换热过程 (4)1.5研究现状 (5)1.5.1国外实验及模拟研究进展 (5)1.5.2国内研究现状和数值模拟 (6)1.5.3管翅式换热器及发展趋势 (8)1.6 管翅式换热器的不同形式的翅片研究现状 (9)2影响翅片换热和压降性能的主要结构因素 (11)2.1翅片间距对换热特性和压降特性的影响 (12)2.2管排数对换热特性和压降特性的影响 (12)2.3管径对换热特性和压降特性的影响 (13)2.4管间距对换热特性和压降特性的影响 (13)3．不同翅片经验关系式总结及比较 (14)3.1 平直翅片经验关系式的总结 (14)3.2 波纹翅片经验关系式的总结 (18)3.3 百叶窗翅片经验关系式的总结 (23)3.4 开缝翅片经验关系式的总结 (26)4．四种翅片经验关系式比较 (31)结论 (38)参考文献 (40)致谢 (44)1 绪论1.1课题背景及研究意义换热器是国民生产中的重要设备，其应用遍及动力、冶金、化工、炼油、建筑、机械制造、食品、医药及航空等各工业部门。
Compact heat exchanger
专利名称：Compact heat exchanger 发明人：WARE CHESTER D.申请号：US19392662申请日：19620511公开号：US3229764A公开日：19660118专利内容由知识产权出版社提供摘要：956,434. Plate type heat exchangers; refrigerators. TRANE CO. Jan. 14, 1963 [May 11, 1962], No. 1616/63. Headings F4H and F4S. A heat exchanger which may be used as a refrigerant evaporator comprises a plurality of first passages 12 for a first fluid, a plurality of second passages for a second fluid, the passages consisting of compartments of rectangular prismatic shape and arranged alternately and separated by heat conducting walls 25, a header 14 to pass internally through each first passage to provide fluid communication between its adjacent second passages so as to provide fluid connection between the second passages in sequence between two of the headers which are used as terminal headers and connected to an inlet or an outlet respectively on the same face of the heat exchanger. Each second passage has an imperforate partition member 24, distributing the fluid as shown in Fig. 3, and substantially centrally disposed to the compartment. In each passage 12 the headers are positioned in-line parallel to the flow of the first fluid, having openings in the floor or ceiling members of the compartments and are positioned centrally with respect to the sides of passage 12. The flow of the first fluid is maintained normal to the flow of the second fluid by fins 28, these fins enhancing the heat transfer between passages (as do perforated fin members 26 in the second passages). Walls 20 and 22 enclose the front and sides of passages 10, withthe side walls 22 extending down the whole side of the complete heat exchanger assembly if desired.申请人：THE TRANE COMPANY更多信息请下载全文后查看。
工程热物理学科境外高水平会议名录
上海交通大学各院系（学科）
重要国际学术会议目录
研究生院汇编
二O一O年十二月
机械与动力学院重要国际学术会议一、顶尖级国际会议（代表本学科领域最高水平的国际会议）
二、A类会议（本学科高水平国际会议）
三、B类会议（学术水平较高、按一定时间间隔规范化、系列性召开的国际会议）
西安交大
能动学院“高水平国际会议”名录
能源与动力工程学院申请增补高水平国际学术会议名录
哈工大
清华大学
热能工程系重要国际学术会议一、A类会议
二、B类会议
航天航空学院（工程热物理）重要国际学术会议一、A类会议
二、B类会议。
浮头式换热器毕业设计
浮头式换热器毕业设计毕业设计（论文）专业：过程装备与控制工程题目：BJS1200浮头式冷凝器设计作者姓名：导师及职称：导师所在单位：二〇一三年六月十六日本科毕业设计（论文）任务书2012 届机械与汽车工程学院过程装备与控制工程专业学生姓名：Ⅰ毕业设计（论文）题目中文：BJS1200浮头式冷凝器设计英文：The design ofBJS1200 floating head condenserⅡ原始资料1. 马小明、钱颂文、朱冬生等. 管壳式换热器[M]，北京：中国石化出版社，2010.2. 董其伍、张垚。
换热器 [M]，北京：化学工业出版社，2008.3.GB_151-1999_管壳式换热器Ⅲ毕业设计（论文）任务内容1、课题研究的意义换热器是国民经济和工业生产领域中应用十分广泛的热量交换设备。
随着现代新工艺、新技术、新材料的不断开发和能源问题的日趋严重，世界各国已普遍把石油化工深度加工和能源综合利用摆到十分重要的位置。
换热器因而面临着新的挑战。
换热器的性能对产品质量、能量利用率以及系统运行的经济性和可靠性起着重要的作用，有时甚至是决定性的作用。
目前在发达的工业国家热回收率已达 96%。
换热设备在现代装置中约占设备总重的 30%左右，其中管壳式换热器仍然占绝对的优势，约 70%。
其余 30%为各类高效紧凑式换热器、新型热管热泵和蓄热器等设备，其中板式、螺旋板式、板翅式以及各类高效传热元件的发展十分迅速。
在继续提高设备热效率的同时，促进换热设备的结构紧凑性，产品系列化、标准化和专业化，并朝大型化的方向发展。
浮头式换热器是管壳式换热器系列中的一种，换热管束包括换热管、管板、折流板、支持板、拉杆、定距管等。
换热管可为普通光管，也可为带翅片的翅片管，翅片管有单金属整体轧制翅片管、双金属轧制翅片管、绕片式翅片管、叠片式翅片管等，材料有碳钢、低合金钢、不锈钢、铜材、铝材、钛材等。
壳体一般为圆筒形，也可为方形。
管箱有椭圆封头管箱、球形封头管箱和平盖管箱等。
英文-甲醇
2002-01-2743 High Efficiency and Low Emissions from a Port-InjectedEngine with Neat Alcohol Fuels Matthew Brusstar, Mark Stuhldreher, David Swain and William PidgeonU. S. Environmental Protection Agency Copyright © 2002 Society of Automotive Engineers, Inc.ABSTRACTOngoing work with methanol- and ethanol-fueled engines at the EPA’s National Vehicle and Fuel Emissions Laboratory has demonstrated improved brake thermal efficiencies over the baseline diesel engine and low steady state NOx, HC and CO, along with inherently low PM emissions. In addition, the engine is expected to have significant system cost advantages compared with a similar diesel, mainly by virtue of its low-pressure port fuel injection (PFI) system. While recognizing the considerable challenge associated with cold start, the alcohol-fueled engine nonetheless offers the advantages of being a more efficient, cleaner alternative to gasoline and diesel engines.The unique EPA engine used for this work is a turbocharged, PFI spark-ignited 1.9L, 4-cylinder engine with 19.5:1 compression ratio. The engine operates unthrottled using stoichiometric fueling from full power to near idle conditions, using exhaust gas recirculation (EGR) and intake manifold pressure to modulate engine load. As a result, the engine, operating on methanol fuel, demonstrates better than 40% brake thermal efficiency from 6.5 to 15 bar BMEP at speeds ranging from 1200 to 3500 rpm, while achieving low steady state emissions using conventional aftertreatment strategies. Similar emissions levels were realized with ethanol fuel, but with slightly higher BSFC due to reduced spark authority at this compression ratio. These characteristics make the engine attractive for hybrid vehicle applications, for which it was initially developed, yet the significant expansion of the high-efficiency islands suggest that it may have broader appeal to conventional powertrain systems. With further refinement, this clean, more efficient and less expensive alternative to today’s petroleum-based IC engines should be considered as a bridging technology to the possible future of hydrogen as a transportation fuel.INTRODUCTIONAlternative fuels, especially alcohol fuels, offer potential to mitigate national security and economic concerns over fuel supplies as well as environmental concerns over tailpipe emissions and resource sustainability. As a result, there has been continuing interest in alternative fuels, heightened recently over proposed legislation that would mandate increases in the use of renewable transportation fuels. Over the last thirty years of automotive research, a variety of alcohol fuels—primarily methanol, ethanol and blends with hydrocarbon fuels—have demonstrated improved emissions of oxides of nitrogen (NOx) and particulate matter (PM) as well as moderately improved brake thermal efficiency [1-4]. Despite this, infrastructure barriers as well as technical challenges, notably cold starting, have limited the widespread use of neat alcohol-fueled vehicles.The benefits and challenges of neat alcohol fuels in PFI applications have been demonstrated in numerous earlier works. Benefits such as higher efficiency and specific power and lower emissions may be realized with alcohols: their high octane number gives the ability to operate at higher compression ratio without preignition [5]; their greater latent heat of vaporization gives a higher charge density [1-3, 6]; and their higher laminar flame speed allows them to be run with leaner, or more dilute, air/fuel mixtures [7]. In addition, alcohols generally give lower fuel heat release rates, resulting in lower NOx emissions and reduced combustion noise [2]. The engine described in the present work uses these inherent advantages of alcohol fuels as the basis for its design and control, thereby enabling attainment of efficiency levels exceeding that of the diesel, with low emissions.One of the main challenges with neat alcohol fuels is cold start emissions, especially in PFI engines [8]. In such applications, the low vapor pressure and lowcetane number must be overcome with higher-energy ignition systems or higher compression ratio [9]. Further, the increased wetting of the intake manifold, cylinder walls and spark plugs must be addressed in the design of the combustion chamber and in the control of transient fueling during startup [8, 10]. Because of these issues, earlier works with PFI SI methanol engines commonly report starting problems below ambient temperatures of about 10o C [8, 11]. With extended periods of cold cranking (i.e., 60 seconds or more), successful starting has been achieved at ambient temperatures as low as –6.5o C [12]. However, these studies were generally performed with lower compression ratio engines, derived from their gasoline counterparts, which are therefore not necessarily optimized for use with neat alcohol fuels. The ongoing work at EPA with high-compression ratio single cylinder PFI SI engines [13], for example, demonstrates the ability to fire on neat methanol during relatively brief cranking at higher speeds, at temperatures as low as 0o C.Earlier work at EPA with alcohol-fueled multi-cylinder engines examined both PFI and DI configurations, generally demonstrating improvements in fuel economy and power, as well as promising cold start emissions. Initial work with a methanol-fueled PFI SI engine [14, 15] yielded fuel economy and emissions that were similar to, but not significantly better than, the baseline gasoline engine. Cold starting was not addressed in that early program, but was instead examined in a follow-on project with a turbocharged, DI, glow-plug-ignited, stratified charge engine [16], based on earlier works showing good cold start performance down as low as –29o C [17]. This project was largely successful, demonstrating good startability and driveability down to –29o C, and producing low FTP emissions of NOx (0.3 g/mi), HC (<0.01 g/mi), CO (0.2 g/mi), PM (0.02 g/mi) and aldehydes (0.002 g/mi) while running lean with a single-stage oxidation catalyst. The measured fuel economy was between 7%-22% better than the baseline gasoline engine, but still slightly lower than the turbocharged diesel.The ongoing PFI alcohol work presented here builds on our earlier experience, and demonstrates better steady state efficiency than the baseline diesel and low emissions with conventional aftertreatment systems, at a significantly lower cost than the diesel. The engine described below runs unthrottled over most of its load range, much like the diesel, but operates with high EGR dilution ratios at stoichiometric fueling, rather than lean and stratified. This strategy takes advantage of the favorable dilute flammability limits of alcohol fuels to operate with lower pumping losses, and uses the high levels of EGR to control knock at high compression ratio. As a result, the engine demonstrates its potential as an efficient, lower cost, renewable fuels alternative to the diesel.EXPERIMENTAL SETUPThe research described below is being conducted under EPA’s Clean Automotive Technology Program, in order to demonstrate feasibility of cleaner, more efficient technologies. The primary focus of the work is on methanol fuel, since it represents the limiting case of oxygenated fuels, at 50% oxygen by mass. Also, its physical properties lend some performance advantages over other alcohols, discussed below. For comparison, however, brake thermal efficiency data with ethanol fuel is also given below, demonstrating similar benefits. ENGINE AND TEST DESCRIPTIONThe engine designed for this work is derived from the 1.9L Volkswagen TDI automotive diesel engine, modified suitably to accommodate port fuel injectors and spark plugs. The stock inlet ports give a swirl ratio of about 2.0, a factor that has been demonstrated to reduce the tendency for knock [18]. Knock was further reduced by modifying the stock combustion chamber to eliminate potential preignition sites. A range of compression ratios from 17:1 to 22:1 were tested in this engine with methanol fuel, although the results reported below were conducted at a nominal compression ratio of 19.5:1. Intake manifold pressure was maintained with a variable geometry turbocharger, which, in turn, also varied the exhaust backpressure on the engine. EGR was metered from the low-pressure side of the turbine to the low-pressure side of the compressor, using a variable backpressure device in the exhaust. The EGR temperature was reduced with a stock Volkswagen water-to-air cooler before the compressor, and the EGR and fresh air were cooled after the compressor with a stock air-to-air intercooler. Together, these compact heat exchangers were able to maintain intake manifold temperatures in the vicinity of 30o C.At least four different types of port fuel injectors were evaluated for measured engine brake thermal efficiency as well as spray characteristics with methanol, verified with high-speed planar laser imaging. The best-atomizing injectors among the group were racing-style, 36 lb/hr, 12-hole port fuel injectors manufactured by Holley, operating at 4 bar rail pressure. For best startup and transient performance, the injector tip was targeted at the back of the intake valve, from a distance of approximately 80 mm.The ignition system consisted of a production Toyota coil with a Champion dual electrode, recessed gap spark plug. High load operation, with a combination of high cylinder pressures and smaller spark advance, placed great demand on both the plugs and coils. Together with higher corrosive properties of methanol, spark plug durability was somewhat of an issue in this testing, as had been witnessed in earlier works [9].Table 1: EPA alcohol engine specifications Engine Type 4 cyl., 4-stroke Combustion Type PFI, SI Displacement 1.9L Valves per cylinder2 Bore79.5 mm Stroke95.6 mm Compression Ratio19.5:1 IVO-344o ATDC* IVC-155 o ATDC* EVO152 o ATDC* EVC341 o ATDC* Bowl Volume18 cc Clearance volume26.4cc Swirl Ratio 2.0 Injectors Holley, 36 lb/hr, 12-holenozzle Rail Pressure 4 bar Spark Plugs Champion recessedgap, dual electrode Turbocharger type Variable geometryExhaust Aftertreatment Ford FFV 2-stage, three-way catalyst*-relative to fired TDCThe engine was run with anhydrous chemical-grade methanol and ethanol fuels, and batch chemical analyses were performed to verify the heating value and density. NOx emissions were measured with a chemiluminescent NOx analyzer, while CO emissions were measured with a non-dispersive infrared analyzer. Unburned hydrocarbon (HC) emissions were measured with a heated flame ionization detector calibrated with propane, but corrected separately for response to methanol and ethanol. A two-stage, three-way Ford FFV catalyst was used for exhaust aftertreatment, and was aged approximately 10 hours at high, variable load prior to testing.ENGINE CONTROLS DESCRIPTIONThe engine controller was a Rapid Prototype Engine Control System (RPECS) provided under contract from Southwest Research Institute. The EPA operating strategy was based on three fundamental principles: (1) High compression ratio, in order to give an expanded dilute operating range; (2) Turbocharging with high levels of EGR, for primary load control and low NOx emissions; (3) Stoichiometric fueling (based on oxygen to fuel), to permit operation with a three-way catalyst. The performance and/or emissions benefits of individual components of this strategy have been demonstrated in earlier works, discussed below. Taken together, however, the present strategy is unique, and presents a path for attaining high levels of efficiency and low emissions in a practical, feasible system.Methanol and ethanol have relatively high octane numbers compared with gasoline; published RON values for methanol and ethanol are between 105-109, compared with about 91-99 for gasoline [19, 20]. As a result, they may be run at a much higher compression ratio, thereby yielding higher engine thermal efficiency. Earlier works with single-cylinder SI methanol engines [5], for example, showed 16% improvement in brake efficiency when raising the compression ratio from 8.0 to 18.0, while still achieving minimum best torque (MBT) spark timing with only light knock. A compression ratio of 19.5:1 was chosen for this work based on earlier experience with a wider range of compression ratios, which showed this to be the best compromise between full spark authority without knock at high load and dilute combustion range at light load. The full spark authority at high load is enabled partly by the relatively high levels of EGR, which has been shown in earlier works to suppress knock at higher compression ratio [21]. Light load stability, meanwhile, is improved by the high compression ratio, which raises the temperature of compression and enhances the already comparatively high flame propagation velocities of the alcohol fuels. As a result, earlier works [21, 22] have demonstrated the ability to operate satisfactorily with as much of 33%-40% EGR with methanol, even with a relatively low compression ratio of 8-8.5. Using a higher compression ratio, the present work was able to achieve nearly 50% EGR without unacceptable cycle-to-cycle combustion variability, using a production spark ignition system.The main objective of the engine load control strategy was to exploit the physical properties of the alcohol fuels in order to run unthrottled, and therefore more efficiently, over a relatively wide range of loads. Methanol-fueled engines using high levels of EGR to modulate load [21-23] have demonstrated efficiency gains of greater than 10% over throttled engines, while giving considerably lower NOx emissions. Combining variable EGR rates with variable intake manifold pressure allows for a wider range of load control. This strategy has also been shown as an effective means of achieving NOx levels below 1.0 g/kW-hr and peak efficiency around 42% in DI, lean stratified-charge methanol engines [23] and similar improvements in PFI lean burn methanol engines [24]. In the present engine, EGR and boost levels are maintained to achieve the best NOx and efficiency, and still enabling MBT (or near MBT) spark timing at high loads. Manifold absolute pressure (MAP) was varied between 1.0-1.5 bar, while the maximum dilution level was limited to about 50% EGR. Throttling, meanwhile, was used only to achieve near-idle loads.The engine is controlled to stoichiometric fueling, enabling use of a three-way catalyst for attainment of emissions at the levels required to achieve Federal Tier II LDV standards. Earlier experience operating lean with an oxidation catalyst [16] showed the ability to achieve Tier II-level emissions on a methanol vehicle for all but NOx, pointing to the need for a three-way catalyst.Operating at stoichiometric has the added benefit of enabling a higher specific power than a similar lean,stratified engine.This strategy was successfully employed to achieve the steady state efficiency and emissions results shown below.RESULTS AND DISCUSSIONGiven below are efficiency and emissions test results for the engine operating with methanol and ethanol.Following this, a brief overview of preliminary cold start testing with methanol is presented.BRAKE THERMAL EFFICIENCY (BTE)The measured BTE of the engine operating with methanol fuel is given below in Figure 1, which may be compared with the BTE of the baseline diesel engine,given in Figure 2.34363840424224681012141650010001500200025003000350040004500B M E P (b a r )RPMFigure 1. Methanol: BTE (%) as a function of BMEP, RPM.The methanol engine exhibits peak efficiency of nearly 43%, and maintains over 40% efficiency over a much wider range of speeds and loads as compared to the diesel engine shown in Figure 2. This region of high efficiency, at levels normally associated with the diesel,extends from 6.5 to more than 15 bar BMEP, from 1200to 3500 rpm. Despite high levels of EGR dilution at light load, combustion variability did not dramatically affect BTE at the BMEP levels shown. In addition, the engine was nearly able to achieve MBT without heavy knock at high loads, due to relatively high dilution with cooled EGR and higher manifold pressure (i.e., higher charge air mass). As a result, the COV of IMEP for the engine operating normally with methanol was less than 3% over the entire range of speeds and loads.Unlike Figure 2, Figure 1 does not show measured BTE for low BMEP, since the focus of the present work was to explore the boundaries of the control strategy outlined earlier in this work. Extending the efficiency map to lower BMEPs with the current engine requires a throttlingdevice, though one that is less restrictive than that for conventional PFI gasoline engines.262830303234363840246810121416B M E P (b a r )RPMFigure 2. Baseline stock 1.9L VW TDI Diesel: BTE (%) as a function of BMEP, RPM.The baseline diesel efficiencies given in Figure 2 were obtained at EPA using a Volkswagen stock TDI engine control unit and stock hardware. The figure shows slightly lower peak efficiency than the PFI methanol engine, and a more rapid drop-off in efficiency with decreasing load. The two major factors that possibly account for this difference are: 1) the parasitic losses of the high-pressure diesel fuel system, and 2) the considerable differences existing in the combustion and heat transfer processes, illustrated clearly by the cylinder pressure versus crank angle comparison given in Figure 3. The figure shows typical pressure traces for the engine operating with diesel and methanol fuel, at 11.5bar BMEP, 2000 rpm, 1.5 bar intake manifold pressure (absolute) and 19.5:1 compression ratio.020*********120-90-60-300306090C y l i n d e r P r e s s u r e (b a r )CAD ATDCMethanol DieselFigure 3. Comparison of cylinder pressure versus crank angle for diesel and methanol engines; 11.5 bar BMEP, 2000 rpm, 1.5 bar intake manifold pressure, 19.5:1 compression ratio.The figure shows that the compression work with methanol is reduced considerably, due to the intense charge cooling resulting from methanol vaporization.Also, the methanol engine exhibits a slower rate of combustion heat release, leading to comparatively lower heat losses.The measured BTE with ethanol fuel is shown below in Figure 4. Both the peak efficiency and the load and speed range with higher efficiency are comparable to that of the diesel in Figure 2. However, the engine was not able to achieve levels of BTE as high as methanol.This was mainly due to knock sensitivity at high load and high speed with ethanol, which prevented the engine from achieving MBT.343638384024681012141650010001500200025003000350040004500B M E P (b a r )RPMFigure 4. Ethanol: BTE (%) as a function of BMEP, RPM.Moreover, the engine experienced greater levels of combustion variability at light load and at higher speeds,as witnessed by the high COV of IMEP shown in Figure 5, which, in turn, reduced the BTE under these conditions. Some of the BTE differential demonstrated here, however, may be recovered by optimizing the compression ratio and calibration for ethanol fuel.BRAKE-SPECIFIC EMISSIONS FOR METHANOL The figures below show NOx and HC emissions for the engine operating with methanol. Similar results are expected for ethanol [25], but are not included.Brake-specific NOx emissions as a function of BMEP and RPM are shown in Figure 6. The high EGR dilution,combined with the slower heat release of methanol yields low levels of NOx, at 0.1-0.2 g/kW-hr over much of the operating map. The NOx emissions increase at lower speed, partly due to the inability of the turbocharger to maintain the intake manifold pressure at a level sufficient to permit higher rates of EGR.2468824681012141650010001500200025003000350040004500B M E P (b a r )RPMFigure 5. Ethanol: COV of IMEP (%) as a function of BMEP, RPM.0.10.20.20.30.40.20.124681012141650010001500200025003000350040004500B M E P (b a r )RPMFigure 6. Brake-specific NOx emissions (g/kW-hr) as a function of speed and load for methanol.Figure 7 below shows brake-specific HC emissions as a function of speed and load. HC emissions are controlled to less than 0.2 g/kW-hr over most of the map, indicating the effectiveness of the aftertreatment system.Brake specific CO measurements are not specifically shown in this work, since they were consistently very low, at less than 0.2 g/kW-hr over the entire map. PM and aldehyde emissions were not measured, though earlier work at EPA with DI methanol engines [16]demonstrated the ability to control these to very low levels with a conventional oxidation catalyst.0.050.10.150.150.224681012141650010001500200025003000350040004500B M E P (b a r )RPMFigure 7. Brake-specific HC emissions (g/kW-hr) as a function of load for methanol.COLD STARTING IN A SINGLE-CYLINDER ENGINE WITH METHANOLThe ongoing research at EPA includes work with single-cylinder engines that simulate closely the characteristics of the multi-cylinder engine. The single-cylinder results presented below were for a PFI SI configuration with 19.5:1 compression ratio and identical cam timings,displacement, bore/stroke ratio, and intake manifold geometry as the multi-cylinder engine described earlier in this work. It was run naturally aspirated and lean, to simulate early stages of the open-loop startup strategy used in the multi-cylinder engine.Cold starting with the single cylinder was examined atambient temperatures from 20o C down to 0oC [13]. The initial fueling and ignition timing sequences were varied to determine optimal combinations to ignite the charge and sustain combustion during the first ten firing cycles.The engine was ramped quickly up to speeds ranging between 1000 rpm to 2000 rpm, simulating conditions commonly seen during startup on the EPA hydraulic hybrid chassis. This higher cranking speed results in a higher compression temperature, and therefore improved low-temperature ignition [26]. Fueling with neat methanol was initiated such that the end of the injection event occurred just prior to intake valve closure.Startability, quantified by the measured IMEP during thefirst ten firing cycles, was very good at 20o C. At 0oC, the measured IMEP and in-cylinder wall temperatures indicated that significant quenching had occurred during the first few firing cycles, yet the engine was able to sustain combustion and achieve load. A more detailed exposition of this topic is planned for a later work.In summary, the results above with methanol- and ethanol-fueled engines exhibit equal or greater efficiency than the comparable diesel engine, and low emissions of NOx, CO and HC. Moreover, preliminary work with cold starting in a single cylinder engine exhibits goodcombustion down at 0oC. These studies are part of theClean Automotive Technology Program at EPA to demonstrate feasibility of clean technologies, and to develop attractive alternatives to conventional-fueled engines.CONCLUSIONThe present work describes a PFI, SI, turbocharged,high compression ratio engine operating with relatively high EGR dilution rates, operating on neat alcohol fuels.From the steady state results presented above, it is concluded that:1. The present engine, optimized for alcohol fuels,exceeds the performance of current conventional-fueled engines, and has potential as a lower-cost alternative to the diesel.2. Brake thermal efficiency levels better than acomparable turbocharged diesel are demonstrated.The engine operating with methanol fuel showed peak BTE of nearly 43%, and a broader high-efficiency operating range than the baseline diesel.3. Emissions of NOx, CO and HC using a conventionalaftertreatment system were shown to be extremely low with methanol, enabling attainment of emissions at the levels required to achieve Federal Tier II LDV standards.4. Brake thermal efficiency with ethanol fuel is alsofavorable compared to that of the baseline diesel engine.5. The present engine offers the potential for a lower-cost renewable fuel alternative to the diesel, by virtue of its less-complex PFI fuel system.ACKNOWLEDGMENTSThe authors appreciate the support of the Laboratory Operations Division at EPA, especially Ron Nicolaus and Aaron Boehlke, for their enthusiastic assistance and maintenance of the test engine.REFERENCES1. M. N. Nabi, et al., “Ultra Low Emission and HighPerformance Diesel Combustion with Highly Oxygenated Fuel”, SAE Paper 2000-01-0231, 2000.2. N. Miyamoto, et al., “Smokeless, Low NOx, HighThermal Efficiency, and Low Noise Diesel Combustion with Oxygenated Agents as Main Fuel,SAE Paper 980506, 1998.3. R. Baranescu, et al., “Prototype Development of aMethanol Engine for Heavy-Duty Application-Performance and Emissions”, SAE Paper 891653,1989.4. B. Dhaliwal, et al., “Emissions Effects of AlternativeFuels in Light-Duty and Heavy-Duty Vehicles”, SAE Paper 2000-01-0692, 2000.5. N. D. Brinkman, “Effect of Compression Ratio onExhaust Emissions and Performance of a Methanol-Fueled Single-Cylinder Engine”, SAE Paper 770791, 1977.6.P. Mohanan, M. K. Gajendra Babu, “A SimulationModel for a Methanol-Fueled Turbocharged Multi-Cylinder Automotive Spark Ignition Engine”, SAE Paper 912417, 1991.7.T. Ryan, S. Lestz, "The Laminar Burning Velocity ofIsooctane, N-Heptane, Methanol, Methane and Propane at Elevated Temperatures and Pressures in the Presence of a Diluent", SAE Paper 800103, 1980.8.V. Battista, et al., “Review of the Cold StartingPerformance of Methanol and High Methanol Blends in Spark Ignition Engines: Neat Methanol”, SAE Paper 902154, 1990.9.K. Hikino, T. Suzuki, “Development of MethanolEngine with Autoignition for Low NOx Emission and Better Fuel Economy”, SAE Paper 891842, 1989. 10.L. G. Dodge, et al., “Development of an Ethanol-Fueled Ultra-Low Emissions Vehicle”, SAE 981358, 1998.11.K. Iwachidou, M. Kawagoe, “Transient UnburnedMethanol and Formaldehyde Emission Characteristics in Cold Operation of a SI Engine Powered by High-Methanol-Content Fuels”, VIII Int.Symp. On Alcohol Fuels, pp. 443-448, Nov. 13-16, 1988.12.N. Iwai, et al., “A Study on Cold Startability andMixture Formation of High-Percentage Methanol Blends”, SAE Paper 880044, 1988.13.D. M. Swain, D. Yerace, Cold-Start HydrocarbonReduction Strategy for Hybrid Vehicles, M. S.Thesis, University of Michigan, 2002.14.W. Clemmens, “Performance of Sequential Port FuelInjection on a High Compression Ratio Neat Methanol Engine”, SAE Paper 872070, 1987.15.C. D. de Boer, et al., “The Optimum Methanol Enginewith Electronic Control for Fuel Efficiency and LowEmissions”, VIII Int. Symp. On Alcohol Fuels, pp.425-430, Nov. 13-16, 1988.16.R. I. Bruetsch, K. H. Hellman, “Evaluation of aPassenger Car Equipped with a Direct Injection Neat Methanol Engine”, SAE Paper 920196, 1992.17.R. M. Siewert, E. G. Groff, “Unassisted Cold Starts to–29 o C and Steady-State Tests of a Direct-Injection Stratified-Charge (DISC) Engine Operated on Neat Alcohols, SAE Paper 872066, 1987.18.W. H. Haight III, P. C. Malte, “Methanol PreignitionTemperature Behavior”, SAE Paper 912414, 1991. 19.R. L. Bechtold, Alternative Fuels Guidebook, SAEInternational, 1997.20.J. B. Heywood, Internal Combustion EngineFundamentals, McGraw-Hill, 1988.21.C. DePetris, et al., “High Efficiency StoichiometricSpark Ignition Engines”, SAE Paper 941933, 1994.22. G. R. Neame, et al., “Improving the Fuel Economyof Stoichiometrically Fuelled S.I. Engines by Means of EGR and Enhanced Ignition—A Comparison of Gasoline, Methanol and Natural Gas”, SAE Paper 952376, 1995.23.Y. Sato, et al., “Combustion and NOx EmissionCharacteristics in a DI Methanol Engine Using Supercharging with EGR”, SAE Paper 971647, 1997.24.G. M. Pannone, R. T. Johnson, “Methanol as a Fuelfor a Lean Turbocharged Spark Ignition Engine”, SAE Paper 8904535, 1989.25.B. Bartunek, et al., “Influence of the Methanol FuelComposition on Performance and Exhaust Emissions of Diesel-Derived Alcohol Engines”, SAE 881197, 1988.26.D. P. Gardiner, M. F. Bardon, “The Effect ofCranking Speed on Cold Starting Performance with Methanol Fuels”, VII Int. Symp. On Alcohol Fuels, pp. 191-195, 1986.。
全热交换英文缩写
全热交换英文缩写The full name of the abbreviation "HE" is heat exchanger.A heat exchanger is a device used to transfer heat between two or more fluids. This can be achieved by using a solid wall to separate the fluids and prevent them from mixing,or by allowing the fluids to mix and transfer heat directly.Heat exchangers are commonly used in a wide variety of applications, including air conditioning, refrigeration, power plants, chemical processing, and many otherindustrial processes. They are also used in everyday appliances such as refrigerators and car radiators.There are several different types of heat exchangers, including shell and tube, plate, and finned tube heat exchangers. Each type has its own advantages and disadvantages, and is suitable for different applications.In a shell and tube heat exchanger, one fluid flows through a series of tubes, while the other fluid flows around the outside of the tubes in a shell. This allows for efficient heat transfer and is commonly used inapplications where one of the fluids is highly viscous or contains solid particles.Plate heat exchangers consist of a series of metal plates with narrow gaps between them. The fluids flow through the gaps, allowing for efficient heat transfer. Plate heat exchangers are compact and lightweight, making them suitable for applications where space is limited.Finned tube heat exchangers are similar to shell and tube heat exchangers, but with the addition of fins on the outside of the tubes. This increases the surface area available for heat transfer, making them suitable for applications where high heat transfer rates are required.Overall, heat exchangers play a crucial role in many industrial processes and everyday appliances, allowing for efficient heat transfer and temperature control."HE"的全称是热交换器。
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~ To whom correspondence should be addressed, at: Air Conditioning and Refrigeration Center, University of Illinois at Urbana-Champaign, Department of Mechanical and Industrial Engineering, 1206 W Green Street, Urbana, IL 61801, USA. * Dedicated to the memory of Gustav Lorentzen.
Les dchangeurs de chaleur compacts et ldgers sont n~cessaires pour les systOmes de conditionnement d'air des vdhicules, ainsi que pour plusieurs ~pes d'dquipement unitaire. L'utilisation pour ces applications du COe, frigorigkne naturel bien adaptd au fonctionnement ~ haute pression est dvalude, et la mise au point d'dchangeurs de chaleur performants est ddcrite. Les dchangeurs de chaleur fonctionnant avec du dio~'de de carbone sont con9us pour un ddbit massique de frigorigbne dlevd et sont munis de tubes de faible diambtre ou de
Development of compact heat exchangers for CO2 air-conditioning systems*
J. Pettersent, A. Hafner and G. Skaugen S1NTEF Energy Research, Refrigeration and Air Conditioning, N-7034 Trondheim, Norway H. Rekstad Norwegian University of Science and Technology, Department of Refrigeration and Air Conditioning, N-7034 Trondheim, Norway
Introduction
At the turn of the century, annual fluorocarbon refrigerant emissions from mobile and unitary airconditioning equipment is likely to pass 100000 metric tonnes ~, corresponding to a global warming impact of more than 150 million metric tonnes of CO2. Even larger indirect CO~ emissions result from the generation of power to drive the systems. The international effort to limit greenhouse gas emissions therefore includes the development of energy-efficient and safe airconditioning systems, preferably based on natural refrigerants with zero global warming potential. With its use of a non-flammable and non-toxic natural fluid, the transcritical carbon dioxide system is a primary candidate for next-generation automobile air conditioning. Since the first publication by Lorentzen and Pettersen six years ago 2, this concept has gained much attention both in industry and academia, and a nearfuture commercial introduction seems possible 3 s. There are also interesting possibilities for using this system in residential air conditioning and heat pumps 6. Successful introduction of CO2-based technology depends on the development of efficient and compact components with low weight, good reliability, and low cost. The mass and space requirements are of particular importance in mobile systems. Heat exchangers account for nearly half of the mass and a major part of the volume for an automotive air-conditioning system (excluding air-handling and heating equipment), and the design and optimization of heat exchangers is therefore very important. Heat exchangers for mobile and unitary equipment are designed with a finned air-side surface and usually have more than 700 m 2 surface area per m 3 core volume. This ratio is the loosely defined limit for a compact heat exchanger 7. The heat exchangers may be mechanically expanded tube-in-fin units or brazed aluminum cores, in both cases various enhancements are used on the air and refrigerant sides. The high working pressure and favorable heat transfer properties of CO2 enable reduced tube diameters and
Received 11 December 1997; revised 16 January 1998; accepted 16 January. 1998
Compact and lightweight heat exchangers are needed for motor vehicle air-conditioning systems and for several types of unitary equipment. The high-pressure natural refrigerant CO 2 is now being evaluated for use in such applications, and efficient heat exchangers are being developed and investigated. Carbon dioxide heat exchangers are designed for high refrigerant mass flux and use small-diameter tubes or extruded fiat microchannel tubes. Refrigerant-side heat transfer coefficients are higher than with fluorocarbons, and reduced internal surface areas can therefore be tolerated. Both small-diameter mechanically expanded round-tube heat exchangers and brazed microchannel-type units have been built and tested successfully. Results show that compact heat exchangers optimized for CO2 are very competitive with baseline HFC/HCFC units in terms of physical dimensions, exchanger mass and thermal performance. Smaller tube and manifold dimensions can give reduced size compared with HFC-134a equipment. The temperature approach between air inlet and refrigerant outlet is much lower in CO2 gas coolers than in baseline system condensers of equal size and capacity, and the reduced refrigerant exit temperature has a marked influence on the coefficient of performance, Microchannel heat exchangers give the best overall efficiency. Refrigerant distribution in multiport manifolds and heat transfer tubes does not seem to be a problem. © 1998 Elsevier Science Ltd and IIR. All rights reserved.