1、更为复杂的系统,其熵值越大,反之,有序或纯配置就是低熵之一。能源已经产生效果的能力,并在下面的章节中所述,可以存储或短暂形式分类。Heat Q is the mechanism that transfers energy across the boundaries of systems with differing temperatures, always toward the lower temperature、 Heat is positive when energy is added to the system、 Work is the mechanism that transfers
2、energy across the boundaries of systems with differing pressures （or force of any kind）, always toward the lower pressure、 If the total effect produced in the system can be reduced to the raising of a weight, then nothing but work has crossed the boundary、 Work is positive when energy is removed fro
3、m the system、 热量Q与不同的温度,跨系统的边界传输能量总就是向温度较低的机制。热就是积极的,当能量被添加到系统中。 功就是指通过存在压差（任一种力）的系统边界传递能量的作用过程,总就是指向低压,如果系统中产生的总效果能被简化为一个重物的提升,那么只有功通过了边界,当能量从系统中一出时,功就是正的。A property of a system is any observable characteristic of the system、 The state of a system is defined by listing its properties、 The most comm
4、on thermodynamic properties are temperature T, pressure p, and specific volume v or density 、 Additional thermodynamic properties include entropy, stored forms of energy, and enthalpy、 Frequently, thermodynamic properties combine to form other properties、 Enthalpy h, a result of combining properties
5、, is defined as: h=u+pv where u is the internal energy per unit mass系统属性就是系统的任何观察到的特征。系统状态的定义就是通过列出其属性。最常见的热力学性质的温度T,压力P,与特定的体积V或密度。其她热力学性质包括熵,能量储存形式,与焓。通常情况下,热力学性质相结合,形成其她属性。焓H,一个属性相结合的结果,被定义为:H = U + PV其中u就是每单位质量的内部能量Each property in a given state has only one definite value, and any property alwa
6、ys has the same value for a given state, regardless of how the substance arrived at that state、 A process is a change in state that can be defined as any change in the properties of a system、 A process is described by specifying the initial and final equilibrium states, the path （if identifiable）, a
7、nd the interactions that take place across system boundaries during the process、 中的每一个给定的状态的属性只有一个定值,与任何财产总就是有相同的值给定的状态,不管如何抵达该国的物质。一个进程就是一个状态的改变,在系统属性的任何改变,可作为定义。一个过程就是指定的初始与最终的平衡状态,路径（如果识别）,并采取跨系统的边界,在这个过程中发生的相互作用。A cycle is a process or a series of processes wherein the initial and final states o
8、f the system are identical、 Therefore, at the conclusion of a cycle, all the properties have the same value they had at the beginning、 A pure substance has a homogeneous and invariable chemical composition、 It can exist in more than one phase, but the chemical composition is the same in all phases一个
9、周期进程的一个过程或一个系列,其中系统的初始与最终状态就是相同的的。因此,在一个周期结束时,所有属性具有相同的价值,她们开始。纯物质均匀的与不变的化学成分。它可以存在于超过一个阶段,但在各个阶段的化学成分就是一样的If a substance is liquid at the saturation temperature and pressure, it is called a saturated liquid、 If the temperature of the liquid is lower than the saturation temperature for the existing
10、pressure, it is called either a subcooled liquid （the temperature is lower than the saturation temperature for the given pressure） or a compressed liquid （the pressure is greater than the saturation pressure for the given temperature）、 如果一种物质在饱与温度与压力的液体,它被称为饱与液体。如果液体的温度低于现有的压力的饱与温度,它被称为就是过冷液体（温度低于给定
11、压力的饱与温度）或压缩液体（压力大于饱与为给定的温度压力）。If a substance exists as a vapor at saturation temperature and pressure, it is called a saturated vapor、 When the vapor is at a temperature greater than the saturation temperature, it is a superheated vapor、 Pressure and temperature of a superheated vapor are independen
12、t properties, because the temperature can increase while pressure remains constant、 Gases such as air at room temperature and pressure are highly superheated vapors、如果一种物质在饱与温度与压力的蒸气存在,它被称为饱与蒸气。当蒸汽温度大于饱与温度,它就是一个热蒸气。过热蒸汽压力与温度就是独立的属性,因为温度增加,而压力保持不变。如在常温常压下空气的气体就是高度过热蒸汽。The second law of thermodynamics
13、 differentiates and quantifies processes that only proceed in a certain direction （irreversible） from those that are reversible、 The second law may be described in several ways、 One method uses the concept of entropy flow in an open system and the irreversibility associated with the process、 The con
14、cept of irreversibility provides added insight into the operation of cycles、 热力学第二定律的区别与量化,只有在某一个方向,就是可逆的（不可逆）进行的过程。第二定律可能在几个方面。一种方法就是使用在一个开放的系统,并与进程关联的不可逆性的熵流的概念。不可逆转的概念到周期的运作提供额外的洞察力。The Carnot cycle, which is completely reversible, is a perfect model for a refrigeration cycle operating between tw
15、o fixed temperatures, or between two fluids at different temperatures and each with infinite heat capacity、 Reversible cycles have two important properties: （1） no refrigerating cycle may have a coefficient of performance higher than that for a reversible cycle operated between the same temperature
16、limits, and （2） all reversible cycles, when operated between the same temperature limits, have the same coefficient of performance卡诺循环,这就是完全可逆的,就是一个完美的模型之间的两个固定的温度,或在不同温度与热容量无限每个的两种流体之间的制冷循环的运行。可逆循环有两个重要的属性:（1）无制冷循环的性能系数之间相同的温度限制经营的可逆循环高于,（2）之间相同的温度极限运行时,所有可逆循环,同样的性能系数Flowing fluids in heating, vent
17、ilating, air-conditioning, and refrigeration systems can transfer heat, mass, and momentum、 This chapter introduces the basics of fluid mechanics related to HVAC processes, reviews pertinent flow processes, and presents a general discussion of single-phase fluid flow analysis、流动的液体在加热,通风,空调与制冷系统,可以传
18、递热量,质量与动量。本章介绍有关暖通空调过程的流体力学,评论相关的流程,基础知识,并提出了一种单相流体流动分析的一般性讨论。Fluids differ from solids in their reaction to shearing、 When placed under shear stress, a solid deforms only a finite amount, whereas a fluid deforms continuously for as long as the shear is applied、 Both liquids and gases are fluids、 Al
19、though liquids and gases differ strongly in the nature of molecular actions, their primary mechanical differences are in the degree of compressibility and liquid formation of a free surface、 In general, liquids are considered incompressible fluids; gases may range from compressible to nearly incompr
20、essible、 流体与固体区别在于她们对剪切力的反应作用。在施加剪切力时,固体只发生有限的变形,而只要有剪切力的作用流体就会连续变形。流体不同于固体剪切她们的反应。当剪切应力下了坚实的变形量只有有限的,而流体的剪切变形。液体与气体都就是流体。虽然液体与气体的分子运动特性有着很大的区别,但就是她们的主要的力学区别在于可压缩性的程度与液体自由表面（界面）的形成。在一般来说,液体被认为就是不可压缩的流体,气体可能范围从可压缩到几乎不可。Viscosity is a measure of a fluids resistance to shear、 Viscous effects are taken
21、into account by categorizing a fluid as either Newtonian or non-Newtonian、 In Newtonian fluids, the rate of deformation is directly proportional to the shearing stress; most fluids in the HVAC industry （e、g、, water, air, most refrigerants） can be treated as Newtonian、 In non-Newtonian fluids, the re
22、lationship between the rate of deformation and shear stress is more complicated、粘度就是流体的抗剪切的措施。考虑采取分类流体为牛顿或非牛顿粘性的影响。在牛顿流体,变形率就是成正比的剪应力;在暖通空调行业（如,水,空气,大部分制冷剂）牛顿流体可以作为治疗。在非牛顿流体,变形与剪切应力率之间的关系更为复杂。Heat is energy in transit due to a temperature difference、 The thermal energy is transferred from one region
23、 to another by three modes of heat transfer: conduction, convection, and radiation、 Heat transfer is among a group of energy transport phenomena that includes mass transfer, momentum transfer or fluid friction and electrical conduction、 热就是由于温差在传输过程中的能量。热能就是从一个地区转移到另一个传热的三种模式:传导,对流与辐射。传热之间的能源运输的现象,其
24、中包括传质,动量传递或流体摩擦与导电。Thermal conduction is the mechanism of heat transfer whereby energy is transported between parts of continuum by the transfer of kinetic energy between particles or groups of particles at the atomic level、 In gases, conduction is caused by elastic collision of molecules; in liquid
25、s and electrically nonconducting solids, it is believed to be caused by longitudinal oscillations of the lattice structure、 Thermal conduction in metals occurs, like electrical conduction, through the motion of free electrons、 Thermal energy transfer occurs in the direction of decreasing temperature
26、、 In solid opaque bodies, thermal conduction is the significant heat transfer mechanism because no net material flows in the process and radiation is not a factor、 热传导传热,使能量就是连续部分之间的运输粒子在原子水平上的颗粒或团体之间的动能转移的机制。气体中,分子的弹性碰撞引起的传导;电导电液体与固体,它被认为就是造成晶格结构的纵向振荡。金属的热传导时,如导电,通过自由电子的运动。热能量转移发生在温度降低的方向。在坚实的不透明机构
27、,热传导就是显著的传热机制,因为没有净物资流动的过程中,辐射就是不就是一个因素。When fluid currents are produced by external sources （for example, a blower or pump）, the solid-to-fluid heat transfer is termed forced convection、 If the fluid flow is generated internally by nonhomogeneous densities caused by temperature variation, the heat
28、transfer is termed natural convection or free convection、当流体的电流就是由外部来源（例如,一个鼓风机或泵）,固 - 液传热被称为强迫对流。如果就是内部所产生的温度变化所造成的非均质密度的流体流动,传热称为自然对流或自然对流。Equation 1 states that the heat flow rate q in the x direction is directly proportional to the temperature gradient dt/dx and the cross-sectional area A normal to the heat flow、 The proportionality factor is the thermal conductivity k、 The minus sign indicates that heat flow is positive the direction of decreasing temperature、 Conductivity values are sometimes given in other units,but consistent uni
