DI86-32 57275782 数字量输入卡原厂 ABB
人们不喜欢通风（局部空气速度超过约100英尺/分钟），
但是在一些炎热的工业环境中
可能需要工作站。辐射效应通常超出
暖通空调设计师的控制，但应在
暖通空调设计。典型的辐射效应是由窗户引起的（冷
冬季，暴露在阳光下时很热），通过照明设备（尤其是
白炽）和在大群体中的人之间的交叉辐射。
辐射效果有时可以通过提供辐射面板来抵消
其根据需要被冷却或加热。有一个有趣的图表
在ASHRAE手册中，该手册绘制了
在任何给定温度下都不满意。它可以解释为：
70至75华氏度之间的一般舒适度范围，但也表明
没有任何温度能让每个人都满意
2.3湿度测量的使用
湿度测量学是研究空气-水蒸气混合物的物理性质，通常称为湿空气。由于空气是大多数空调过程中的终能量传输介质，因此它是
暖通空调设计中的基本工具。19章讨论了湿度
原则和更详细的讨论可在ASHRAE手册基本原理中找到。3.许多不同的湿度图
可从各种来源获得。本书使用了ASHRAE图表
和桌子。
作者（海恩斯）绘制了高空湿度图
在20世纪50年代，用于他的设计工作
随时可用。图表的格式与
该时期的ASHRAE海平面图。几个的表格值
高度是手工计算的，手工绘图技术是：
习惯于
ASHRAE现在有一张海拔5000英尺的海图。
2.4暖通空调循环
图2.1是基本机械系统的示意图
冷却循环。虽然除湿不是系统的重要组成部分
暖通空调工程基础：2部分
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暖通空调工程基础：2部分17
图2.1机械冷却循环。
冷却循环，通常发生在冷却介质较冷的地方
比空气的露点温度高。中的冷负荷QC
调节空间是内部和外部负载（例如。，
人、灯、太阳能），通常通过循环空气去除
其中进入的空气具有比期望的空间条件更低的温度和湿度。为了抵消冷却负荷
送风的温度和湿度增加到相等
然后空气返回空气处理装置
空气处理机组（AHU），其中空气被再冷却和除湿。大多数空间需要
一些（外部）通风空气，与回流空气混合
空气处理机组，从而施加额外的冷却负荷QV。如果外部空气焓小于空间焓，则QV将为负，并将获得一些“自由冷却”。需要工作能量
使空气循环，通常是由电动机驱动的风扇，以及
该功QW成为冷却负荷的一部分。由QCQV QW表示的总负荷必须通过散热去除
设备，通常是制冷系统。一些额外的工作是
这里通过泵送液体和驱动制冷机来完成
冷凝器或冷却塔风扇。终，所有这些热能都是
倾倒到散热器中，有时是水，通常是大气。
请注意，工作部分
DI86-32 57275782 数字量输入卡原厂 ABB
DI86-32 57275782 数字量输入卡原厂 ABB
people do not like a draft (local air velocity over about 100 ft/min),
but in some hot industrial environments, a high rate of airflow at the
workstation may be necessary. Radiant effects are often beyond the
control of the HVAC designer but should be taken into account in the
HVAC design. Typical radiant effects are caused by windows (cold in
winter, hot when exposed to the sun), by lighting fixtures (especially
incandescent), and by cross-radiation among people in large groups.
Radiant effects can sometimes be offset by providing radiant panels
which are cooled or heated as needed.1 There is an interesting graph
in the ASHRAE Handbook which plots the percentage of people who
are dissatisfied at any given temperature. It can be interpreted to read
a range of general comfort between 70 and 75F, but it also shows that
there is no temperature at which everybody will be satisfied.2
2.3 Use of Psychrometrics
Psychrometrics is the study of the physical properties of air-water vapor mixtures, commonly called moist air. Because air is the final energy transport medium in most air conditioning processes, it is an
essential tool in HVAC design. Chapter 19 discusses psychrometric
principles, and a more detailed discussion can be found in the ASHRAE Handbook Fundamentals.3 Many different psychrometric charts
are available from various sources. This book uses the ASHRAE charts
and tables.
The author (Haines) constructed high altitude psychrometric charts
in the 1950s, for use in his design work when such charts were not
readily available. The charts were made to the same format as the
ASHRAE sea-level chart of that period. Tabular values for several
altitudes were hand calculated and hand-drafting techniques were
used.
ASHRAE now has a chart for 5000-ft elevation above sea level.
2.4 HVAC Cycles
Figure 2.1 is a schematic representation of an elementary mechanical
cooling cycle. While dehumidification is not an essential part of the
HVAC Engineering Fundamentals: Part 2
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HVAC Engineering Fundamentals: Part 2 17
Figure 2.1 Mechanical cooling cycle.
cooling cycle, it usually occurs where the cooling medium is colder
than the dew point temperature of the air. The cooling load QC in the
conditioned space is a combination of internal and external loads (e.g.,
people, lights, solar) and is usually removed by circulating air through
the space, with the entering air having a lower temperature and humidity than the desired space condition. To offset the cooling load, the
temperature and humidity of the supply air are increased to equal
those of the space, and then air is returned to the air-handling unit
(AHU), where it is recooled and dehumidified. Most spaces require
some (outside) ventilation air, which is mixed with the return air at
the AHU, thereby imposing an additional cooling load QV . If the outside-air enthalpy is less than the space enthalpy, then QV will be negative and some ‘‘free cooling’’ will be obtained. Work energy is required
to circulate the air—usually a fan driven by an electric motor—and
this work QW becomes a part of the cooling load. The total load represented by QC QV QW must be removed by the heat rejection
equipment, usually a refrigeration system. Some additional work is
done here by pumping fluids and driving refrigeration machines and
condenser or cooling-tower fans. Ultimately all this heat energy is
dumped to a heat sink—sometimes water, most often atmospheric air.
Note that the work portions
DI86-32 57275782 数字量输入卡原厂 ABB
