AKM52K-ANC2DB00 ANC2DB00 伺服电动机 Kollmorgen
与流体的密度和流体柱的高度有关。静态压力在所有方向上施加相等。
流动流体的速度压力与平方成正比
流体速度；i、 即速度倍增，速度压力倍增。
管道中流动的流体的摩擦损失与
速度的平方。
移动流体所需的泵送功率与
流体密度和粘度，以及处理的流体体积
以及流体被泵送的压力。
由于摩擦损失与流量的平方成正比
定义系统中的泵送功率与
流量的立方。
出于暖通空调目的，空气被视为不可压缩流体。
对于不可压缩流体，封闭系统中的流体量为
常数任何流出都必须被等价的流入抵消，或者
系统中保持的流体量必须发生变化。这是
质量守恒定律允许我们考虑流体在
就像我们在银行里数钱一样。详见参考文献3
讨论这个主题。
*另见16章。
暖通空调工程基础：1部分
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暖通空调工程基础：1部分7
1.6热力学*
热力学与物质的热特性有关
与宇宙的自然亲和力，从更高到更高
低能量状态。热力学研究物质的能力
接受能量水平的变化（将比热作为一种特性）
并将焓作为能量水平的测量尺度）。为此
在提醒段落中，请记住：
物质的能量接受能力称为比热
英制单位为Btu每磅每华氏度。水
比热为1.0 Btu/（lb F）是佳的受热介质之一。
相位变化中的能量接受能力称为
从液体到气体（即水到蒸汽）的蒸发潜热
以及从液体到固体（即水到冰）的熔化潜热。
同样，水的蒸发潜热约为
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。
二
AKM52K-ANC2DB00 ANC2DB00 伺服电动机 Kollmorgen
AKM52K-ANC2DB00 ANC2DB00 伺服电动机 Kollmorgen
ional to the density of the fluid and to the height of the fluid column. Static pressure is exerted equally in all directions.
The velocity pressure of a flowing fluid is proportional to the square
of the fluid velocity; i.e., doubling the velocity quadruples the velocity pressure.
The friction loss of a fluid flowing in a conduit is proportional to the
square of the velocity.
The pumping power required to move a fluid is proportional to the
fluid density and viscosity, as well as the volume of fluid handled
and the pressure against which the fluid is pumped.
Since the friction loss is proportional to the square of the flow, the
pumping power in a defined system is proportional overall to the
cube of the flow rate.
For HVAC purposes, air is considered to be an incompressible fluid.
For incompressible fluids, the amount of fluid in a closed system is
constant. Any outflows must be offset by equivalent inflows, or there
must be a change in the amount of fluid held in the system. This is
the Law of Conservation of Mass and allows us to account for fluid in
a process just as we count money in the bank. See Ref. 3 for further
discussion of this topic.
*See also Chap. 16.
HVAC Engineering Fundamentals: Part 1
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HVAC Engineering Fundamentals: Part 1 7
1.6 Thermodynamics*
Thermodynamics has to do with the thermal characteristics of matter
and with the natural affinity of the universe to go from a higher to a
lower energy state. Thermodynamics deals with the ability of matter
to accept changes in energy level (relates to specific heat as a property
and to enthalpy as a scale of measurement of energy level). For this
reminder paragraph, remember:
The energy acceptance capacity of a substance is called specific heat
with English units of Btu per pound per degree Fahrenheit. Water
with a specific heat of 1.0 Btu/ (lb F) is one of the best heataccepting media.
The energy acceptance capacity in a change of phase is called the
latent heat of vaporization from liquid to gas (i.e., water to steam)
and latent heat of fusion from liquid to solid (i.e., water to ice).
Again, 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
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