焓湿图(中英文)开放版

CLM believes that it is incumbent on manufacturers to serve the industry by regularly disseminating information gathered through laboratory research, testing programs, and field experience.

The CLM Air Conditioning Clinic series is one means of knowledge sharing. It is intended to acquaint a technical audience with various fundamental aspects of heating, ventilating, and air conditioning (HVAC). We have taken special care to make the clinic as uncommercial and straightforward as possible. Illustrations of CLM products only appear in cases where they help convey the message contained in the accompanying text.

This particular clinic introduces the reader to psychrometry, the science concerned with the physical laws that govern air – water mixtures.

CLM认为，制造商有责任通过定期传播通过实验室研究，测试程序和现场经验收集的信息来为行业服务。

CLM空调章节系列是知识共享的一种方式。旨在使技术人员熟悉加热，通风和空调（HVAC）的各个基本方面。我们已采取特殊措施，使章节尽可能地减少商业性和直接性。 CLM产品的插图仅在它们有助于传达随附文本中包含的信息的情况下出现。

这家特殊的章节向读者介绍了湿度法，这是一门管理空气-水混合物的物理定律的科学。

Psychrometry is the science dealing with the physical laws of air – water

mixtures.

When designing an air conditioning system, the temperature and moisture content of the air to be conditioned, and the same properties of the air needed to produce the desired air conditioning effect, must be known. Once these properties are known, the air conditioning task can be determined. This analysis can be performed using the psychrometric chart. The psychrometric chart graphically displays several physical properties of air over a broad range of conditions. Knowing the relationship of these air properties aids the task of air conditioning system design and analysis.

干湿法是一门处理空气-水混合物的物理定律的科学。

在设计空调系统时，必须知道要调节的空气的温度和水分含量，以及产生所需的空调效果所需的空气的相同特性。一旦知道了这些属性，就可以确定空调任务。可以使用湿度表执行此分析。湿度图以图形方式显示了在各种条件下空气的几种物理性质。了解这些空气特性之间的关系有助于空调系统的设计和分析。

Properties of Air

At first glance, the psychrometric chart appears to be an imposing network of lines. When properly used, however, it provides valuable information about the properties of air. During this session, the psychrometric chart and its use in solving many air conditioning problems will be explained.

空气特性

乍一看，干湿图似乎是一个很复杂的网络。但是，如果使用得当，它可以提供有关空气特性的有价值的信息。在本节中，将解释湿度计及其在解决许多空调问题中的用途。

The psychrometric chart contains five physical properties to describe the characteristics of air:

湿热图包含五个描述空气特征的物理特性：

? Dry-bulb temperature 干球温度

? Wet-bulb temperature 湿球温度

? Dew-point temperature 露点温度

? Relative humidity 相对湿度

? Humidity ratio 含湿量

Dry-bulb temperatures are read from an ordinary thermometer that has a dry bulb. 干球温度是从带有干球的普通温度计中读取的。

Wet-bulb temperatures are read from a thermometer whose bulb is covered by a wet wick. The difference between the wet-bulb temperature and the dry-bulb temperature is caused by the cooling effect produced by the evaporation of moisture from the wick. This evaporation effect reduces the temperature of the bulb and, therefore, the thermometer reading.

Consequently, the difference between dry-bulb and wet-bulb temperature readings is a measure of the dryness of air. The drier the air, the greater the difference between the dry-bulb and wet-bulb readings.

从温度计上读取湿球温度，该温度计的球被湿的芯子覆盖。湿球温度和干球温度之间的差异是由棉芯中水分蒸发产生的冷却效果引起的。这种蒸发作用会降低灯泡的温度，从而降低温度计的读数。

因此，干球温度读数和湿球温度读数之间的差异是空气干燥度的量度。空气越干燥，干球和湿球读数之间的差异就越大。

The third property, dew-point temperature, is the temperature at which moisture leaves the air and condenses on objects, just as dew forms on grass and plant leaves.第三个特性是露点温度，是水分离开空气并凝结在物体上的温度，就像露水在草和植物的叶子上形成时一样。

When the dry-bulb, wet-bulb, and dew-point temperatures are the same, the air is saturated. It can hold no more moisture. When air is at a saturated condition, moisture entering the air displaces moisture within the air. The displaced moisture leaves the air in the form of fine droplets. When this condition occurs in nature, it is called fog.干球，湿球和露点温度相同时，空气饱和。它不能容纳更多的水分。当空气处于饱和状态时，进入空气的水分会取代空气中的水分。排出的水分以细小水滴的形式离开空气。自然界中发生这种情况时，称为雾。

The fourth property, relative humidity, is a comparison of the amount of moisture that a given amount of air is holding, to the amount of moisture that the same amount of air can hold, at the same dry-bulb temperature.第四个特性，相对湿度，是在相同的干球温度下，给定空气量所保持的水分量与相同量空气所能保持的水分量的比较。

Relative humidity is expressed as a percentage. For example, if the relative humidity of the air is 50%, it contains one-half the amount of moisture possible at the existing dry-bulb temperature.

Finally, humidity ratio describes the actual weight of water in an air – water vapor mixture. In other words, if one kilogram of air were wrung completely dry, comparing the weight of the water to the weight of the dry air would yield its humidity ratio. Humidity ratio can be expressed as grams of moisture per kilogram of dry air.最后，含湿量描述了空气-水蒸气混合物中水的实际重量。换句话说，如果将一公斤的空气完全干燥，将水的重量与干燥的空气的重量进行比较将得出其含湿量。

含湿量可以表示为每千克干燥空气中的水分克数。

When any two of these five properties of air are known, the other three can be quickly determined from the psychrometric chart. (Exception: If only dew-point temperature and humidity ratio are known, one other property must be known in order to determine the remaining two.)当空气的这五个属性中的任何两个已知时，其他三个可以从湿度表中快速确定。（例外：如果仅知道露点温度和湿度比，则必须知道另一个特性才能确定其余两个特性。）

For example, let's assume that the summer design conditions are 35°C dry bulb and 25°C wet bulb.

What is the relative humidity, humidity ratio, and dew point?

例如，假设夏季设计条件是35°C干球和25°C湿球。

相对湿度，湿度比和露点是多少？

Only one point on the psychrometric chart represents air with both of these conditions. This point is located where the vertical 35°C dry-bulb (DB) and diagonal 25°C wet-bulb (WB) temperature lines intersect.

From this intersection, the remaining three air properties can be read from the chart. The humidity-ratio lines are horizontal and the values are shown on the right side of the chart. In this example, the humidity ratio is about 16 grams of moisture per kilogram of dry air.

Notice that the point of intersection falls between two relative humidity curves: 40% and 50%. By interpolation, the relative humidity at this condition is approximately 46%. Some psychrometric charts include a dew-point temperature scale on the right-hand side of the chart. If a separate scale is not provided, the dew-point temperature can be determined by drawing a horizontal line from the point until it intersects with the saturation curve (100% relative humidity). Then, draw a vertical line down from that intersection to the dry-bulb temperature scale along the horizontal axis. For this example condition, the dew-point temperature is approximately 21°C.

Constructing a Simple Psychrometric Chart

To better understand the psychrometric chart and show why the lines intersect as they do, we will construct a simple chart.

The amount of moisture contained in saturated air depends on dry-bulb temperature. This table shows the maximum amount of water vapor that one kilogram of dry air can hold at various dry-bulb temperatures. For example, at 5°C, one kilogram of dry air can absorb and hold 5.42 grams of water; at 15°C it can absorb 10.69 grams; at 25°C it can absorb 20.17 grams; and so on. Each of these conditions is a saturation point.

构造简单的湿度图

为了更好地理解干湿图并显示线为何如此相交，我们将构建一个简单的图。

饱和空气中的水分含量取决于干球温度。该表显示了在各种干球温度下一公斤干燥空气可以容纳的最大水蒸气量。例如，在5°C下，一千克的干燥空气可以吸收并容纳5.42克水；在15°C下可以吸收10.69克; 在25°C下可以吸收20.17克；等等。这些条件中的每一个都是一个饱和点。

These saturation points can be plotted on a chart with dry-bulb temperature along the horizontal axis and humidity ratio along the vertical axis.

When several saturation points are plotted, the curve created resembles the relative humidity curves of the psychrometric chart.

这些饱和点可以绘制在图表上，干球温度沿水平轴，湿度比沿垂直轴。

当绘制几个饱和点时，创建的曲线类似于干湿图的相对湿度曲线。

In fact, this curve forms the 100% relative-humidity curve or saturation curve. All points on this curve represent the moisture content that constitutes complete saturation of air at the various dry-bulb temperatures.实际上，该曲线形成了100％相对湿度曲线或饱和度曲线。该曲线上的所有点都代表了水分含量，这些水分含量构成了各种干球温度下空气的完全饱和。

Another fact about saturated air should be discussed before we proceed. Assume a volume of moist air has the initial conditions indicated in column

D of the table. The air has a 30°C dry-bulb temperature and a 15°C dew point.

A wet-bulb thermometer shows the wet-bulb temperature to be 20.1°C. From a moisture-content table, the relative humidity of the air is approximately 40%.

With no change in the moisture content of this volume of air, the table shows the progressive change that occurs as the air cools.

Point C: As the dry-bulb temperature drops from 30°C to 25°C, the wet-bulb temperature drops from 20.1°C to 18.5°C, yet the dew point remains the same at 15°C. The relative humidity rises from 40% to 54%.

Point B: When the dry-bulb temperature reaches 20°C, the wet-bulb temperature is about 16.8°C, the dew point remains constant at 15°C, and the relative humidity is 73%.

Point A: Finally, when the dry-bulb temperature reaches the 15°C dew-point temperature, the wet bulb cannot be reduced any lower because evaporation can no longer occur: the air is saturated and contains all the moisture it can hold. The relative humidity is now 100%.

At any point on a 100% relative-humidity curve, the three air temperatures—dry bulb, wet bulb and dew point—are equal.

在继续之前，应该讨论有关饱和空气的另一个事实。假设一定量的潮湿空气具有表D列中指示的初始条件。空气的干球温度为30°C，露点为15°C。湿球温度计显示的湿球温度为20.1°C。根据水分含量表，空气的相对湿度约为40％。

Additionally, the dew-point temperature does not change as the dry-bulb temperature changes, provided that the moisture content of the air remains the same. Merely heating the air does not change its moisture content. Therefore, as the air is heated, its condition will move horizontally along a constant humidity-ratio line.

In this example, heating 15°C saturated air moves the air condition along a horizontal humidity-ratio line that corresponds to a constant 10.65 grams of moisture per kilogram of dry air.

Horizontal lines can be drawn from each saturation point across to the right side of the chart. A horizontal line can be provided for each humidity-ratio value.另外，露点温度不会随着干球温度的变化而变化，只要空气中的水分含量保持不变即可。仅加热空气不会改变其水分含量。因此，当空气被加热时，其状态将沿着恒定的湿度比线水平移动

。

在此示例中，加热15°C的饱和空气会沿水平湿度比率线移动空调，该湿度比率线对应于每千克干燥空气恒定的10.65克水分。

可以从每个饱和点到图表的右侧绘制水平线。可以为每个湿度比率值提供一条水平线。

Additional curves can be added to the chart to represent relative humidity

conditions that are less than 100%. The curves shown are at 10% intervals and represent humidity conditions ranging from completely saturated air to completely dry air. When air is completely dry, its relative humidity cannot change with temperature. The 0% condition is therefore represented by the horizontal axis of the chart.

可以将其他曲线添加到图表中，以表示小于100％的相对湿度条件。所示曲线以10％的间隔，代表从完全饱和空气到完全干燥空气的湿度条件。空气完全干燥后，其相对湿度不会随温度变化。因此，0％条件由图表的水平轴表示。