Ans: d 34. These pressures are divided or separated in the system by the compressor's discharge valve and the metering device. It is therefore important that the refrigerant has a low freezing point … 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. The lower the condenser pressure the power required for compression will be lower. High Pressure, High Temperature B. Vapor Refrigeration/Heat Pump Cycle. Ch 10, Lesson B, Page 2 - The Ideal Vapor-Compression Refrigeration Cycle. Its function is to provide a heat transfer surface through which heat can pass from the refrigerated space into the vaporizing refrigerant. In other words, it is the transfer of heat from a cold reservoir to a hot one. Q1. in the actual cycle due to fluid friction and heat transfer [4] Thermal Lab manual, Aerospace Engineering Depart- to or from surroundings. Ans: d 34. Condensation. 4. The sub-cooling in a refrigeration cycle. If you are not acquainted with the system, you may need to conduct a few tests to pinpoint the issue. The Coefficient of Performance (COP) expresses the efficiency of this cycle. You could also perform a freeze test if finding the exact point becomes troublesome. There are several pressure-controlling devices to take care of this requirement. Compressors themselves can be scroll, screw, centrifugal or reciprocating types. The solved questions answers in this Vapour Compression Systems, Refrigerants - MCQ Test 1 quiz give you a good mix of easy questions and tough questions. The desirable properties of a refrigerant are as follows: 1. Refrigerant Pressures The typical vapor compression refrigeration system (as shown in Figure 1) can be divided into two pressures. While some people have viewed this method as environmentally harmful and inefficient, the cycle is still applicable in the industrial sphere. In this cycle, a circulating refrigerant such as R134a enters a compressor as low-pressure vapor at or slightly below the temperature of the refrigerator interior. 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. Understanding the vapor compression cycle is a critical step towards countering common industrial refrigeration problems. Throttling valves play two crucial roles in the vapor compression cycle. Water treatment practices need to be on point to keep this problem at bay. 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. Read : In Part (a), we can determine the COP of the Carnot refrigeration cycle directly from the [temperatures of the two thermal reservoirs. Other possible improvement approaches for your system include installation of high efficiency system components cooling tower upgrades. Chapter 10: Refrigeration Cycles The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. The highest temperature during the cycle, in a vapour compression system, occurs after. 2. Expansion. Ideal vapour compression refrigeration cycle The impracticalities of the reversed Carnot Cycle can be eliminated by: vaporising the refrigerant completely before it is compressed Since the vapor compression cycle is against the Second Law of Thermodynamics, some work is necessary for the transfer to take place. The simplest explanation of this system is a heat engine working in reverse, technically referred to as reverse Carnot engine. Refrigerant is the life blood of the vapor compression cycle. The resulting refrigerant vapor returns to the compressor inlet at point 1 to complete the thermodynamic cycle. Evaporation. This is the series of articles that describes various important parts of the refrigerators and air-conditioners. It gives real time results that help you identify the problem as shown by temperature changes. The specific heat of liquid should be as small as possible and of vapour should be as high as possible to give less superheating of vapour. The vapor compression cycle circulates a fluid through a compressor, condenser, expansion valve, and evaporator, in order to absorb heat from a refrigerated space at a low temperature and give off heat at a higher temperature to the surroundings, thus keeping the refrigerated space cool. The refrigerant (for example R-717) enters the compressor at low temperature and low pressure. They are condensing and evaporating - or high- and low-side - pressures. The refrigerant for a refrigerator should have (a) high sensible heat (b) high total heat (c) high latent heat (d) low latent heat (e) low sensible heat Ans: c 26. Evaporator. It condenses and evaporates at temperatures and pressures close to the atmospheric conditions. A more detailed explanation of the steps is as explained below. 4. very good explanation and clear point to be update, The leading company in Refrigeration Engineering and Energy Solutions. The condenser operates at 1.6 MPa and the evaporator operates at 300 kPa. 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