工程热力学和制冷循环外文翻译本科学位论文Word文档格式.docx

1、 240112608 班 级： K 暖通 111 Class: K-Nuantong111 所在学院： 康尼学院 College: Kangni College 专 业： 建筑环境与设备工程 Profession: Building Environment and Equipment Engineering 指导教师： Tutor: Liu Minghui 2015年 3月 7日 CHAPTER 1THERMODYNAMICS AND REFRIGERATION CYCLES THERMODYNAMICS . 1.1 First Law of Thermodynamics . 1.2 Seco

2、nd Law of Thermodynamics . 1.2 Thermodynamic Analysis of Refrigeration Cycles . 1.3 Equations of State . 1.3 Calculating Thermodynamic Properties . 1.4 COMPRESSION REFRIGERATION CYCLES . 1.6 Carnot Cycle . 1.6 Theoretical Single-Stage Cycle Using a Pure Refrigerant or Azeotropic Mixture . 1.8 Lorenz

3、 Refrigeration Cycle . 1.9 Theoretical Single-Stage Cycle Using Zeotropic Refrigerant Mixture . 1.10 Multistage Vapor Compression Refrigeration Cycles . 1.10 Actual Refrigeration Systems . 1.12 ABSORPTION REFRIGERATION CYCLES . 1.14 Ideal Thermal Cycle . 1.14 Working Fluid Phase ChangeConstraints .

4、1.14 Working Fluids . 1.15 Absorption Cycle Representations . 1.16 Conceptualizing the Cycle . 1.16 Absorption Cycle Modeling . 1.17 Ammonia-Water Absorption Cycles . 1.19 Nomenclature for Examples . 1.20THERMODYNAMICS is the study of energy, its transformations, and its relation to states of matter

5、. This chapter covers the application of thermodynamics to refrigeration cycles. The first part reviews the first and second laws of thermodynamics and presents methods for calculating thermodynamic properties. The second and third parts address compression and absorption refrigeration cycles, two c

6、ommon methods of thermal energy transfer.THERMODYNAMICSA thermodynamic system is a region in space or a quantity of matter bounded by a closed surface. The surroundings include everything external to the system, and the system is separated fromthe surroundings by the system boundaries. These boundar

7、ies can be movable or fixed, real or imaginary. Entropy and energy are important in any thermodynamic system. Entropy measures the molecular disorder of a system. The more mixed a system, the greater its entropy; an orderly or unmixed configuration is one of low entropy. Energy has the capacity for

8、producing an effect and can be categorized into either stored or transient forms.Stored EnergyThermal （internal） energy is caused by the motion of molecules and/or intermolecular forces.Potential energy （PE） is caused by attractive forces existing between molecules, or the elevation of the system. （

9、1）wherem =massg = local acceleration of gravityz = elevation above horizontal reference planeKinetic energy （KE） is the energy caused by the velocity of molecules and is expressed as （2）where V is the velocity of a fluid stream crossing the system boundary.Chemical energy is caused by the arrangemen

10、t of atoms composing the molecules.Nuclear （atomic） energy derives from the cohesive forces holding protons and neutrons together as the atoms nucleus.Energy in TransitionHeat Q is the mechanism that transfers energy across the boundaries of systems with differing temperatures, always toward the low

11、er temperature. Heat is positive when energy is added to the system （see Figure 1）.Work is the mechanism that transfers 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

12、to the raising of a weight, then nothing but work has crossed the boundary. Work is positive when energy is removed from the system （see Figure 1）.Mechanical or shaft work W is the energy delivered or absorbed by a mechanism, such as a turbine, air compressor, or internal combustion engine.Flow work

13、 is energy carried into or transmitted across the system boundary because a pumping process occurs somewhere outside the system, causing fluid to enter the system. It can bemore easily understood as the work done by the fluid just outside the system on the adjacent fluid entering the system to force

14、 or push it into the system. Flow work also occurs as fluid leaves thesystem.Flow work =pv （3）where p is the pressure and v is the specific volume, or the volume displaced per unit mass evaluated at the inlet or exit.A property of a system is any observable characteristic of the system. The state of

15、 a system is defined by specifying the minimum set of independent properties. The most common 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

16、 properties combine to form other properties. Enthalpy h is an important property that includes internal energy and flow work and is defined as （4）where u is the internal energy per unit mass.Each property in a given state has only one definite value, and any property always has the same value for a

17、 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）, and the interactions that tak

18、e place across system boundaries during theprocess.A cycle is a process or a series of processes wherein the initial and final states of the system are identical. Therefore, at the conclusion of a cycle, all the properties have the same value they had at the beginning. Refrigerant circulating in a c

19、losed system undergoes acycle.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.If a substance is liquid at the saturation temperature and pressure,it is called a saturated liquid. If th

20、e temperature of the liquid is lower than the saturation temperature for the existing 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 th

21、e given temperature）.When a substance exists as part liquid and part vapor at the saturation temperature, its quality is defined as the ratio of the mass of vapor to the total mass. Quality has meaning only when the substance is saturated （i.e., at saturation pressure and temperature）.Pressure and t

22、emperature of saturated substances are not independent properties.If a substance exists as a vapor at saturation temperature and pressure, it is called a saturated vapor. （Sometimes the term dry saturated vapor is used to emphasize that the quality is 100%.）When the vapor is at a temperature greater

23、 than the saturation temperature, it is a superheated vapor. Pressure and temperature of a superheated vapor are independent properties, because the temperature can increase while pressure remains constant. Gases such as air at room temperature and pressure are highly superheated vapors.FIRST LAW OF

24、 THERMODYNAMICSThe first law of thermodynamics is often called the law of conservation of energy. The following form of the first-law equation is valid only in the absence of a nuclear or chemical reaction.Based on the first law or the law of conservation of energy for any system, open or closed, th

25、ere is an energy balance asNet amount of energy Net increase of stored=added to system energy in systemorEnergy in Energy out = Increase of stored energy in systemFigure 1 illustrates energy flows into and out of a thermodynamic system. For the general case of multiple mass flows with uniform proper

26、ties in and out of the system, the energy balance can be written （5）where subscripts i and f refer to the initial and final states,respectively.Nearly all important engineering processes are commonly modeled as steady-flow processes. Steady flow signifies that all quantities associated with the syst

27、em do not vary with time. Consequently, （6）where h = u + pv as described in Equation （4）.A second common application is the closed stationary system for which the first law equation reduces to （7）SECOND LAW OF THERMODYNAMICSThe second law of thermodynamics 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