The refrigerant returns to the state at the inlet of the evaporator by expanding adiabatically through a turbine. Heat pump and refrigeration cycles and systems gate and. Refrigeration is the science of moving heat from low temperature to high temperature. Recognize materials used in halocarbon refrigeration systems that are not appropriate for use with ammonia due to material incompatibilities 3. Another wellknown refrigeration cycle is the gas refrigeration cycle in which the refrigerant remains in the gaseous phase throughout. 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. Chapter 10 refrigeration cycles ideal and actual vapor.
It is not a suitable model for refrigeration cycles since processes 23 and 41 are not practical. This chapter presents an outline of modem refrigeration thermodynamics, with an emphasis on low. 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. Steam enters the turbine at 10 mpa and 500c and is cooled in the condenser at a pressure of 10 kpa. A second method of producing low temperatures is by using a closed cycle cooling system.
Review chapter 10 chapter 10 refrigeration and heat pump systems 10. 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. A free powerpoint ppt presentation displayed as a flash slide show on id. The simple gas refrigeration cycle analysis is as follows. Analysis a in an ideal vaporcompression refrigeration cycle, the compression process is isentropic, the. Refrigeration air conditioning and heat pumps fifth edition. In this process, from state 3 to state 4, the temperature decreases from th to tc, and there is a decrease in pressure. Show the cycle on a ts diagram with respect to saturation lines, and determine a the. Refrigeration advanced engineering thermodynamics wiley. Chapter 10 class powerpoint thermodynamics chapter 10. Thermodynamically renewable energybased cycles do not contain a mechanical compression process. Analyze the ideal vaporcompression refrigeration cycle.
A twostage cascade refrigeration cycle is shown in fig. An ideal gas refrigeration cycle using air as the working fluid operates between the pressure limits of 80 kpa and 240 kpa. It is then throttled to the evaporator pressure and vaporizes as it absorbs heat from the refrigerated space. The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. For the doublecascade system shown, it is important that the triplestate temperature of the. Chapter 11 refrigeration cycles study guide in powerpoint to accompany thermodynamics. If you are a student using this manual, you are using it without permission. 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. This heattransfer process occurs in nature without requiring any devices. The above figure shows the objectives of refrigerators and heat pumps. Unit 8 leak detection system evacuation and cleanup.
The purpose of a refrigerator is the removal of heat, called the cooling load, from a lowtemperature medium. Chapter 10 refrigeration cycles s assumptions 1 steady operating. Analyze the reheat and regenerative vapor power cycles. 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. Pdf air conditioning and refrigeration by rex miller. The vaporcompression refrigeration cycle process 41. In refrigeration cycles, energy is transferred q from a cold point to a hot point as heat.
Refrigeration cycles the vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. When the cooling power is in the range of kilowatts the cooling system. The ordinary vaporcompression refrigeration systems are simple, inexpensive, reliable, and practically maintenancefree. The purpose of a refrigerator is the removal of heat, called the. 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. Rev pages chapter 9 refrigerants, refrigeration cycles, and. Chapter 10 refrigeration and heat pump systems vaporcompression refrigeration cycle most common refrigeration cycle in use. Identify key safety considerations when using ammonia as a refrigerant 2.
In addition to chilling and freezing applications, refrigeration technology is applied in air conditioning and heat pumps. Analyze vapor power cycles in which the working fluid is alternately vaporized and condensed. Tables a11 analysis a from the refrigerant4a tables discussionthe cooling load decreases by 4. Thermodynamics 7 refrigeration and heat pump systems vaporcompression refrigeration cycle evaporator eq. The reverse process, however,cannot occur by itself. The purpose of a refrigerator is the removal of heat, called the cooling load, from a low. The thermal efficiency of a carnot heat engine is 30%. Find cop r, cop r, carnot for same t max and t min, and the tons of refrigeration. Liquefaction and refrigeration systems springerlink. 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. The carnot cycle is the most efficient cycle operating between two specified temperature limits but it is not a suitable model for power cycles. Chapter 10 refrigeration cycles assumptions 1 steady. Evaporator compressor condenser expansion valve most common refrigeration cycle in use today twophase liquidvapor mixture. The purpose of a refrigeration system is to maintain a cold region at a temperature below the temperature of its surroundings.
Chapter iii closed cycle refrigerators and cryocoolers. Saturated vapor enters the compressor at 100c, and saturated liquid leaves the condenser at 280c. 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. Consider a 210mw steam power plant that operates on a simple ideal rankine cycle.
Chapter iii closed cycle refrigerators and cryocoolers 1. 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. Other refrigeration cycles discussed in this chapter are cascade refrigeration, where. Yeah, it seems complicated at first, but it will be easier to understand. A power cycle or heat engine generates work using an energy source at a high. Figure 10 1 is the typical performance curves for a compressor. Analyze power generation coupled with process heating called cogeneration. The two methods are the cascade and the multistage vapor compression refrigeration cycles. Introduce the concepts of refrigerators and heat pumps and the measure of their performance. In this cycle a unit mass of fluid is subjected to four processes after which it returns to its original state. 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. Refrigeration and air conditioning career councillor.
Whereas the vc cycle is a work powered cycle, absorption is a heat powered cycle. Assuming the water is maintained at 10 c in the evaporator, the evaporator pressure will be the. Therefore, a cascade refrigeration system with a different refrigerant at the bottoming cycle is recommended in this case. Chapter 10 examples 1 an ideal vaporcompression refrigerant cycle operates at steady state with refrigerant 4a as the working fluid. Figure 10 shows two singlestage systems in cascade which enabl. Cycles an from a high nk at a rat to drive a sothermal. Boleslecturenotesthermodynamicschapter10 chapter 10. Refrigeration systems and applications wiley online books.
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. Differentiate directexpansion, gravity flooded, and liquid overfeed evaporator arrangements 4. 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. Pdf chapter 11 refrigeration cycles anne alle academia. Chapter 10 refrigeration cycles win 1\q12 mpa 45 4 ql s and win nih2 hi 0. An open cycle refrigeration system is that the system is without a traditional evaporator. Boles lecture notes thermodynamics chapter 10 chapter 10.
The best cop will be given by a cycle which is a carnot cycle operating between the given temperature. Discuss the operation of refrigeration and heat pump systems. The ideal vaporcompression cycle consists of four processes. 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. 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. Review the factors involved in selecting the right refrigerant for an application. Investigate ways to modify the basic rankine vapor power cycle to increase the cycle thermal efficiency. Boles a free powerpoint ppt presentation displayed as a flash slide show on id.
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 two methods are the cascade and the multistage vapor compression refrigeration. Refrigeration, air conditioning and heat pumps 5th edition. Maae 2400 thermodynamics and heat transfer chapter 10 class notes refrigeration cycles carleton university department of. Chapter 10 examples solution 1 an ideal vaporcompression refrigerant cycle operates at steady state with refrigerant 4a as the working fluid. The vapour compression cycle is used for refrigeration in preference to gas cycles. Analyze the actual vaporcompression refrigeration cycle. Microsoft powerpoint chapter 10a refrigeration cycles. 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. Thermodynamics of engineering system the carnot vapor cycle ts diagram of two carnot vapor cycles. Introduction in chapter ii we described the principles of liquefaction of gases to produce low temperatures. Compression cycle an overview sciencedirect topics. Roll your mouse over the lesson title to see a brief description of the. Chapter 10 refrigeration cycles 10 3 ideal and actual vaporcompression cycles 10 4c yes.
Such refrigeration cycles are called cascade refrigeration cycles. Refrigeration, air conditioning and heat pumps, fifth edition, provides a comprehensive introduction to the principles and practice of refrigeration. 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 simple vaporcompression refrigeration cycle is the most widely used refrigeration cycle, and it is adequate for most refrigeration applications. 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. T he refrigerant of the system is an open flow and is. Devices that produce refrigeration are called refrigerators, and the cycles on which they operate are called refrigeration cycles. The rate of heat removal from the refrigerated space, the power input to the compressor, the rate of heat rejection. The rate of heat removal from the refrigerated space. Vaporcompression refrigeration cycle there are four principal control volumes involving these components. Sep 12, 2016 this chapter presents an outline of modem refrigeration thermodynamics, with an emphasis on low. 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 other facility or to a storage tank. The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a.
The transfer of heat from a lowtemperature region to a hightemperature one. The carnot cycle is difficult to achieve in a practical system. The refrigerant leaves the evaporator 20oc and has a condenser pressure of 0. An actual vaporcompression refrigeration cycle differs from the ideal one in several ways. In this lesson, we study two methods to increase the coefficient of performance of the simple vaporcompression vc refrigeration cycle. The reversed carnot, an ideal cycle, is the most efficient refrigeration cycle, to which other cycles are compared in terms of efficiency. 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. 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. 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. A carnot refrigeration cycle absorbs heat at 12 c and rejects it at. An ideal reversible cycle based on the two temperatures of the system can be drawn on a temperatureentropy basis.
608 633 705 278 435 644 1181 797 1501 1447 1383 1143 788 278 1456 1554 810 176 1564 1249 689 309 215 506 1476 478 10 343 688 287 514 1467 840