Stages of the Vapor-Compression Refrigeration Cycle The Vapor-Compression Refrigeration Cycle is comprised of four steps. In a vapour compression cycle, the refrigerant immediately after expansion valve is (a) liquid (b) sub-cooled liquid (c) saturated liquid (d) wet vapour (e) dry vapour. Other possible improvement approaches for your system include installation of high efficiency system components cooling tower upgrades. In a vapour compression system, the lowest temperature during the cycles occurs after. They are condensing and evaporating - or high- and low-side - pressures. 34. Water treatment practices need to be on point to keep this problem at bay. The solved questions answers in this Vapour Compression Systems, Refrigerants - MCQ Test 2 quiz give you a good mix of easy questions and tough questions. Often, manufacturers will tear down returned compressors in search faults. The sub-cooling in a refrigeration cycle. The condenser operates at 1.6 MPa and the evaporator operates at 300 kPa. The above figure shows the objectives of refrigerators and heat pumps. Classification of refrigerant: Fluids suitable for refrigeration purposes can be classified into primary and secondary refrigerants. The condensing temperature is 48 oC, and the evaporating temperature is -18 oC. As the name implies, these systems belong to the general class of vapour cycles, where in the working fluid (refrigerant) undergoes phase change at … Vapor-compression refrigeration is one of the many refrigeration cycles available for use. The motor is easily the highest energy consumer in the vapor compression cycle. The highest temperature during the cycle, in a vapour compression system, occurs after. Copyright © 2020 Bright Hub PM. Ideal vapour compression refrigeration cycle The impracticalities of the reversed Carnot Cycle can be eliminated by: vaporising the refrigerant completely before it is compressed It’s even ok if the compressor feed is slightly superheated. While some people have viewed this method as environmentally harmful and inefficient, the cycle is still applicable in the industrial sphere. That’s means it should have high coefficient of performance and consume less power for producing certain refrigerating effect. There is no ideal refrigerant that can be used in all the conditions. Most coolants are designed so that they have relatively high vapor pressures at typical application temperatures to avoid the need to maintain a significant vacuum in the refrigeration cycle. Regular checks of the chiller logs should unearth any anomaly, specifically the comparison between amperage and voltage. These pressures are divided or separated in the system by the compressor's discharge valve and the metering device. Hence it is vital that the refrigerants used in refrigeration and air-conditioning systems should be non-toxic in nature, so that even if they are leaked in the atmosphere they won’t have any damaging effects to human life. Water for example cannot be used below 0 Deg C. Low Condensing Pressure. 5. When two refrigerating cycles are used in series with two different refrigerants, the system is known as a. dual refrigeration system b. cascade refrigeration system c. vapour absorption refrigeration system d. none of the above View Answer / Hide Answer Over years of studies, some common reasons for compressor failure have been identified to include lubrication problems, overheating, slugging, flood back and contamination. Compression. Low freezing point: When the refrigerant goes through the expansion valve in the refrigeration cycle, it experiences a tremendous pressure drop and hence a tremendous decrease in temperature as well. Presently, ammonia is the only toxic refrigerant being used to a large extent though its applications are limited to packing plants, ice plants and large cold storage facilities. What is its defining feature of these systems? in the actual cycle due to fluid friction and heat transfer [4] Thermal Lab manual, Aerospace Engineering Depart- to or from surroundings. Compressors themselves can be scroll, screw, centrifugal or reciprocating types. Ans: d 35. Vapor Compression Refrigeration | Refrigeration HVAC Vapor compression refrigeration typically involves a refrigerant which includes R-134A, R-22, and R-410A are the common types of refrigerants used in HVAC now. Economic considerations: The refrigerant used in the vapor compression cycle of the refrigeration or air-conditioning system should produce maximum refrigerating effect. Condensation. Since specific heat is high in vapor phase so temperature rise of f vapor after vaporization of liquid refrigerant … There are are four important parts of the refrigerators and air-conditioners, these are: compressor, condenser, expansion valve and evaporator. At this stage of the Vapor Compression Refrigeration Cycle, the refrigerant is at a lower temperature than its surroundings. As this problem increases head pressure, it can lead to increased energy use by the compressor. First, they maintain a pressure differential between low- and high-pressure sides. The most common include ammonia, Freon (and other chlorofluorocarbon refrigerants, aka CFCs), and HFC-134a (a non-toxic hydrofluorocarbon). It has been and is the most widely used method for air conditioning of large public buildings, private residences, hotels, hospitals, theaters, restaurants and automobiles. 2. Evaporation. Compression. Vapor Compression Refrigeration System A vapour compression refrigeration system is an improved type of air refrigeration system in which a suitable working substance, termed as refrigerant, is used. Many issues could lead to this- blocked air filters, dirty air passages etc. Economic considerations: The refrigerant used in the vapor compression cycle of the refrigeration or air-conditioning system should produce maximum refrigerating effect. We also share information about your use of our site with our social media, advertising and analytics. Vapour Compression Refrigeration Cycle - MCQs with Answers Q1. Compression. Earlier refrigerants had very damaging effects for the atmosphere, but now a number of new and safe refrigerants have been discovered and are fast replacing the older ones. Vapor Compression Refrigeration System A vapour compression refrigeration system is an improved type of air refrigeration system in which a suitable working substance, termed as refrigerant, is used. Here, compression takes place to raise the temperature and refrigerant pressure. However, contrary to HFCs, its GWP is negligible when applied as a refrigerant. Question: When Operating A Refrigerator On The Vapour Compression Cycle The Compressor Operates In The Superheat Region Of The Pressure - Enthalpy Diagram. Mechanical Engineering students definitely take this Vapour Compression Systems, Refrigerants - MCQ Test 2 exercise for a better result in the exam. Refrigerant Pressures The typical vapor compression refrigeration system (as shown in Figure 1) can be divided into two pressures. If you are a refrigeration technician and you encounter low evaporator pressure, one of the areas to check is the liquid line, specifically for any form of restriction. Here are certain properties that all refrigerants should possess so that they can be considered for use in refrigeration and air-conditioning systems: Safe properties: The refrigerants that are used in refrigerating and air-conditioning systems should be harmless to the environment and not contribute to the depletion of the ozone layer, or to the increase in earth’s warming potential also called the greenhouse effect. That’s means it should have high coefficient of performance and consume less power for producing certain refrigerating effect. These units lie in close proximity to human beings, and technicians frequently come in contact with the refrigerants. Chapter 10: Refrigeration Cycles The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. Since the vapor compression cycle is against the Second Law of Thermodynamics, some work is necessary for the transfer to take place.