S72402S-NANANA 输入模块用于控制传输速度 Kollmorgen
ain，蒸发潜热约为
1000 Btu/lb和144 Btu/lb的熔化潜热非常好
在恒定温度下涉及大量能量的
相变。
热力学可用于检查制冷循环
使用数学工具和技术分析
设备和系统。
热力学一定律说“能量守恒”对于
就金钱而言，我们可以考虑能源投入、产出和
存储热力学与流体力学的结合使我们
计算背负在流体流上的能量流
信心。
热力学二定律说，能量留给自己
总是从高到低，从快到慢，从暖到冷。
要使事情向上发展，否则，我们必须消耗能量。
没有永动机这样的东西。
湿度测量学是热力学的一个专业，涉及湿空气（空气和水蒸气的混合物）的物理。参见参考文献4
本主题的进一步讨论。
1.7传热†
在研究热传递时，我们研究通过质量运动的能量
通过传导，通过对流从固体到移动液体，或
通过辐射从一个物体到另一个物体。记得：
*另见17章。
†另见18章。
暖通空调工程基础：1部分
下载自数字工程图书馆@McGraw-Hill（www.digitalengineeringlibrary.com）
版权所有©2004麦格劳-希尔公司。版权所有。
任何使用均受网站上给出的使用条款的约束。
8.一章
热量总是从较暖的地方转移到较冷的地方，无一例外。
传导和对流的传热与驱动温差成正比。差价加倍
以使传热速率加倍（T1T2）。
辐射传热与
对温差 tem-4中的小变化（T T）。1 2
温度可以在辐射传热速率中产生相对较大的变化。
对于流体之间的传热，逆流（相反方向）是
这比平行流（同一方向）更有效。
减少热传递的隔热层遵循收益递减定律，即所用隔热层数量的倒数，例如。一缘
S72402S-NANANA 输入模块用于控制传输速度 Kollmorgen
S72402S-NANANA 输入模块用于控制传输速度 Kollmorgen
ain, water with a latent heat of vaporization of approximately
1000 Btu/ lb and a latent heat of fusion of 144 Btu/ lb is very good
at involving large quantities of energy at constant temperature in
the phase change.
Thermodynamics can be used to examine the refrigeration cycles
with mathematical tools and techniques to analyze performance of
equipment and systems.
The first law of thermodynamics says that ‘‘energy is conserved.’’ For
matter as for money, we can account for energy inputs, outputs, and
storage. Combining thermodynamics with fluid mechanics allows us
to calculate energy flows piggybacked onto fluid flows with accuracy
and confidence.
The second law of thermodynamics says that energy left to itself
always goes from high to low, from fast to slow, from warm to cold.
To make things go uphill, to go otherwise, we must expend energy.
There is no such thing as a perpetual-motion machine.
Psychrometrics is a specialty of thermodynamics involving the physics of moist air, a mixture of air and water vapor. See Ref. 4 for
further discussion of this topic.
1.7 Heat Transfer†
In studying heat transfer, we study energy in motion—through a mass
by conduction, from a solid to a moving liquid by convection, or from
one body to another through space by radiation. Remember:
*See also Chap. 17.
†See also Chap. 18.
HVAC Engineering Fundamentals: Part 1
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
8 Chapter One
Heat is transferred from warmer to colder—always, without exception.
Heat transfer for conduction and for convection is directly proportional to the driving temperature differential. Double the difference
to double the heat transfer rate (T1 T2).
Heat transfer by radiation is proportional to the fourth power of the
absolute temperature difference Small changes in tem- 4 4 (T T ). 1 2
perature can create relatively large changes in radiation heat transfer rates.
For heat transfer between fluids, counterflow (opposite direction) is
much more effective than parallel flow (same direction).
Insulation to reduce heat transfer follows a law of diminishing returns, the reciprocal of the amount of insulation used, for instance,. . The first insulatio
S72402S-NANANA 输入模块用于控制传输速度 Kollmorgen
