Boleslecturenotesthermodynamicschapter10 chapter 10. In this lesson, we study two methods to increase the coefficient of performance of the simple vaporcompression vc refrigeration cycle. The best cop will be given by a cycle which is a carnot cycle operating between the given temperature. The rate of heat removal from the refrigerated space. The two cycles are connected through the heat exchanger in the middle, which serves as the evaporator for the topping cycle cycle a and the condenser for the bottoming cycle cycle. The purpose of a refrigerator is the removal of heat, called the cooling load, from a lowtemperature medium. Find cop r, cop r, carnot for same t max and t min, and the tons of refrigeration. The rate of heat removal from the refrigerated space, the power input to the compressor, the rate of heat rejection to the environment, and the cop are to be determined. The ideal vaporcompression cycle consists of four processes.
Boles lecture notes thermodynamics chapter 10 chapter 10. The carnot cycle is difficult to achieve in a practical system. Rev pages chapter 9 refrigerants, refrigeration cycles, and. A carnot refrigeration cycle absorbs heat at 12 c and rejects it at. The vapour compression cycle is used for refrigeration in preference to gas cycles. Refrigeration cycles the vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. Tables a11 analysis a from the refrigerant4a tables discussionthe cooling load decreases by 4. Refrigeration is the science of moving heat from low temperature to high temperature. Refrigeration air conditioning and heat pumps fifth edition. The purpose of a refrigerator is the removal of heat, called the. Evaporator compressor condenser expansion valve most common refrigeration cycle in use today twophase liquidvapor mixture. Chapter 10 refrigeration cycles assumptions 1 steady. An actual vaporcompression refrigeration cycle differs from the ideal one in several ways.
Refrigeration and air conditioning career councillor. The two methods are the cascade and the multistage vapor compression refrigeration. The purpose of a refrigerator is the removal of heat, called the cooling load, from a low. Thermodynamics of engineering system the carnot vapor cycle ts diagram of two carnot vapor cycles. Clear and comprehensive, it is suitable for both trainee and professional hvac engineers, with a straightforward approach that also helps inexperienced readers gain a comprehensive introduction to the fundamentals of the technology. In addition to chilling and freezing applications, refrigeration technology is applied in air conditioning and heat pumps.
The thermal efficiency of a carnot heat engine is 30%. The simple vaporcompression refrigeration cycle is the most widely used refrigeration cycle, and it is adequate for most refrigeration applications. Mechanical refrigeration works by changing the the majority of heat is removed from the the majority of the works by removedchanging the absorbed heat is state of the refrigerant. The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a. Refrigeration advanced engineering thermodynamics wiley. The basic refrigeration cycle for beginners if you are interested in learning how a refrigeration system works, it is helpful to understand from the ph pressure enthalpy chart perspective.
Review the factors involved in selecting the right refrigerant for an application. Discuss the operation of refrigeration and heat pump systems. Microsoft powerpoint chapter 10a refrigeration cycles. Chapter 10 refrigeration engineering thermodynamics scribd. This heattransfer process occurs in nature without requiring any devices. A twostage cascade refrigeration cycle is shown in fig.
Chapter 10 refrigeration and heat pump systems vaporcompression refrigeration cycle most common refrigeration cycle in use. Chapter 10 examples solution 1 an ideal vaporcompression refrigerant cycle operates at steady state with refrigerant 4a as the working fluid. Thermodynamic cycles are broadly classified as power and refrigeration cycles. Chapter 10 refrigeration cycles 10 4 10 11 an ideal vaporcompression refrigeration cycle with refrigerant4a as the working fluid is considered. The reversed carnot, an ideal cycle, is the most efficient refrigeration cycle, to which other cycles are compared in terms of efficiency. Analyze the reheat and regenerative vapor power cycles. The ordinary vaporcompression refrigeration systems are simple, inexpensive, reliable, and practically maintenancefree. Identify key safety considerations when using ammonia as a refrigerant 2. Chapter 11 refrigeration cycles study guide in powerpoint to accompany thermodynamics. The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. Assuming the water is maintained at 10 c in the evaporator, the evaporator pressure will be the. Analyze the ideal vaporcompression refrigeration cycle. Maae 2400 thermodynamics and heat transfer chapter 10 class notes refrigeration cycles carleton university department of.
In refrigeration cycles, energy is transferred q from a cold point to a hot point as heat. Differentiate directexpansion, gravity flooded, and liquid overfeed evaporator arrangements 4. Such refrigeration cycles are called cascade refrigeration cycles. In this cycle a unit mass of fluid is subjected to four processes after which it returns to its original state. However, real refrigeration and liquefaction systems are made up of similar processes which are usually compared in their performance to that of the ideal carnot cycle. Chapter iii closed cycle refrigerators and cryocoolers. Other refrigeration cycles discussed in this chapter are cascade refrigeration, where. Show the cycle on a ts diagram with respect to saturation lines, and determine a the.
In this process, from state 3 to state 4, the temperature decreases from th to tc, and there is a decrease in pressure. Refrigeration, air conditioning and heat pumps, fifth edition, provides a comprehensive introduction to the principles and practice of refrigeration. Thermodynamically renewable energybased cycles do not contain a mechanical compression process. Chapter 10 refrigeration cycles 10 3 ideal and actual vaporcompression cycles 10 4c yes. Another wellknown refrigeration cycle is the gas refrigeration cycle in which the refrigerant remains in the gaseous phase throughout. Chapter iii closed cycle refrigerators and cryocoolers 1. Refrigeration systems and applications wiley online books. Carnot refrigeration cycle this cycle is obtained by reversing the carnot vapor power cycle the schematic and accompanying t s diagram is showing the carnot refrigeration cycle operating between a region at temperature t c and another region at a higher temperature. Figure 10 1 is the typical performance curves for a compressor. Steam enters the turbine at 10 mpa and 500c and is cooled in the condenser at a pressure of 10 kpa. Chapter 10 refrigeration cycles win 1\q12 mpa 45 4 ql s and win nih2 hi 0. If you are a student using this manual, you are using it without permission.
Analyze the actual vaporcompression refrigeration cycle. In an ideal vaporcompression refrigeration cycle, the refrigerant enters the compressor as a saturated vapor and is cooled to the saturated liquid state in the condenser. Unit 8 leak detection system evacuation and cleanup. Since the carnot vapor refrigeration cycle is made up of internally reversible processes, areas on the t s diagram can be interpreted as heat transfers. Analysis a in an ideal vaporcompression refrigeration cycle, the compression process is isentropic, the. Therefore, a cascade refrigeration system with a different refrigerant at the bottoming cycle is recommended in this case. Whereas the vc cycle is a work powered cycle, absorption is a heat powered cycle. The two methods are the cascade and the multistage vapor compression refrigeration cycles. The refrigerant leaves the evaporator 20oc and has a condenser pressure of 0. Recognize materials used in halocarbon refrigeration systems that are not appropriate for use with ammonia due to material incompatibilities 3.
Chapter 10 refrigeration cycles ideal and actual vapor. The reversed carnot cycle is the most efficient refrig. The two cycles are connected through the heat exchanger in the middle, which serves as the evaporator for the topping cycle cycle a and the condenser for the bottoming cycle cycle b. The maximum cop of a refrigeration cycle operating between temperature limits of tl and th actual refrigeration cycles are not as efficient as ideal ones like the carnot cycle because of the irreversibilities involved. Introduce the concepts of refrigerators and heat pumps and the measure of their performance. The presentation is structured to show the steady progress made toward lower temperatures, more efficient and advanced refrigeration installations, and, overall, a more powerful thermodynamics. Refrigeration cycles chap111 work input of a carnot heat pump consider a heat pump that operates on the reversed carnot cycle with r4a as the working fluid executed under the saturation dome between the pressure limits of 140 kpa and 800 kpa. A free powerpoint ppt presentation displayed as a flash slide show on id. The transfer of heat from a lowtemperature region to a hightemperature one. Thermodynamics 7 refrigeration and heat pump systems vaporcompression refrigeration cycle evaporator eq.
Analyze power generation coupled with process heating called cogeneration. Recent experience shows that because of low availability of renewable energy, this approach could be realized in the most effective manner for refrigeration and heat pumping techniques. The suction gas for the refrigeration system might be from a storage tank or from a pipeline, the refrigeration system is to liquefy the gas and send the liquid to. The above figure shows the objectives of refrigerators and heat pumps. Pdf air conditioning and refrigeration by rex miller. The conventional vapour compression refrigeration systems cannot be effectively used for lowtemperature applications because the power consumed by the compressor is largely increased, and hence for lowtemperature applicatireservoir and cycle i working fluid, cycon, a cng the analysis of refrigeration heat pump cyascaded refrigeration system is used. Review chapter 10 chapter 10 refrigeration and heat pump systems 10. Investigate ways to modify the basic rankine vapor power cycle to increase the cycle thermal efficiency. Finite time thermodynamics of cascaded refrigeration and heat. The simple gas refrigeration cycle analysis is as follows. Saturated vapor enters the compressor at 100c, and saturated liquid leaves the condenser at 280c.
The purpose of a refrigeration system is to maintain a cold region at a temperature below the temperature of its surroundings. Roll your mouse over the lesson title to see a brief description of the. A second method of producing low temperatures is by using a closed cycle cooling system. Chapter 10 class powerpoint thermodynamics chapter 10. This chapter presents an outline of modem refrigeration thermodynamics, with an emphasis on low. Refrigeration, air conditioning and heat pumps 5th edition. The vaporcompression refrigeration cycle process 41. The refrigerant returns to the state at the inlet of the evaporator by expanding adiabatically through a turbine. Liquefaction and refrigeration systems springerlink. Chapter 2 the refrigeration cycle chapter 3 refrigerants chapter 4 compressors chapter 5 oil in refrigerant circuits chapter 6 condensers and cooling towers chapter 7 evaporators chapter 8 expansion valves chapter 9 controls and other circuit components chapter 10 component selection and balancing. The rate of heat removal from the refrigerated space, the power input to the compressor, the rate of heat rejection. T he refrigerant of the system is an open flow and is. Chapter 10 examples 1 an ideal vaporcompression refrigerant cycle operates at steady state with refrigerant 4a as the working fluid.
This chapter describes the fundamentals of refrigeration. Analyze vapor power cycles in which the working fluid is alternately vaporized and condensed. For the doublecascade system shown, it is important that the triplestate temperature of the. The cop for a reversible refrigeration cycle, such as the carnot cycle, is defined by, 1 rrev 1 hl cop tt. The lowest temperature of this cycle is answer a 44 c chap118 power input for a gas helium refrigeration cycle consider an ideal gas refrigeration cycle using. Cycles an from a high nk at a rat to drive a sothermal. An open cycle refrigeration system is that the system is without a traditional evaporator.
Chapter 11 refrigeration cycles 607 a major application area of thermodynamics is refrigera tion, which is the transfer of heat from a lower temper ature region to a higher temperature one. Changing any one of the three components might change the shape of the triangle and therefore, changes the character and the capacity of the system. Vaporcompression refrigeration cycle there are four principal control volumes involving these components. Pdf chapter 11 refrigeration cycles anne alle academia. An ideal reversible cycle based on the two temperatures of the system can be drawn on a temperatureentropy basis.
Finite time thermodynamics of cascaded refrigeration and. Figure 10 shows two singlestage systems in cascade which enabl. Introduction in chapter ii we described the principles of liquefaction of gases to produce low temperatures. Sep 12, 2016 this chapter presents an outline of modem refrigeration thermodynamics, with an emphasis on low. The reversed carnot cycle both cops increase as the difference between the two temperatures decreases, that is, as t l rises or t h falls. It is then throttled to the evaporator pressure and vaporizes as it absorbs heat from the refrigerated space. It is not a suitable model for refrigeration cycles since processes 23 and 41 are not practical. Devices that produce refrigeration are called refrigerators, and the cycles on which they operate are called refrigeration cycles. The reverse process, however,cannot occur by itself. Consider a 210mw steam power plant that operates on a simple ideal rankine cycle. When the cooling power is in the range of kilowatts the cooling system.
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