That’s means it should have high coefficient of performance and consume less power for producing certain refrigerating effect. 3. Second, they control the amount of liquid refrigerant entering the evaporator. Mechanical Engineering students definitely take this Vapour Compression Systems, Refrigerants - MCQ Test 1 exercise for a better result in the exam. This is again very important to ensure the safety of humans that are using the refrigerating and air-conditioning systems. Therefore, it evaporates and absorbs latent heat of vaporization. They are condensing and evaporating - or high- and low-side - pressures. High Pressure, High Temperature B. It is a compression process, whose aim is to raise the refrigerant pressure, as it flows from an evaporator. There are several pressure-controlling devices to take care of this requirement. Refrigerants should have low freezing point than the normal operating conditions. For different temperature conditions and applications different refrigerants are found to be suitable. 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. Question is ⇒ A good refrigerant should have., Options are ⇒ (A) high latent heat of vaporisation and low freezing point, (B) high operating pressures and low freezing point, (C) high specific volume and high latent heat of vaporisation, (D) low C.O.P. Condensation. Vapor compression refrigeration systems are used for a variety of cooling/refrigeration applications. The above figure shows the objectives of refrigerators and heat pumps. The refrigerant (for example R-717) enters the compressor at low temperature and low pressure. As the refrigerant flows through the condenser, it is in a constant pressure. Refrigerant Pressures The typical vapor compression refrigeration system (as shown in Figure 1) can be divided into two pressures. A refrigerant should have low latent heat If operating temperature of system is low, then refrigerant with low boiling point should be used Precooling and subcooling bf refrigerant are same Superheat and sensible heat of a. refrigerant are same It is therefore important that the refrigerant has a low freezing point … If you are not acquainted with the system, you may need to conduct a few tests to pinpoint the issue. 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. Throttling valves play two crucial roles in the vapor compression cycle. All the contents you mentioned in post is too good and can be very useful. Q1. In a vapour compression cycle, the refrigerant immediately after expansion valve isAns: a 25. It is in a gaseous state. Since many years a number of chlorofluorocarbons (CFCs) have been used as the refrigerants that cause excessive damage to the ozone layer when they are leaked to the atmosphere. Specifically, pressure control is paramount for safety and efficiency reasons. 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. Ans: d 34. The sub-cooling in a refrigeration cycle. 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. As this problem increases head pressure, it can lead to increased energy use by the compressor. All the components involved in the cycle have the potential to disrupt efficiency or overall functionality of the system altogether. Condensation. As the name implies, these systems belong to the general class of vapour cycles, where in the working fluid (refrigerant) undergoes phase change at … Since specific heat is high in vapor phase so temperature rise of f vapor after vaporization of liquid refrigerant … At this stage of the Vapor Compression Refrigeration Cycle, the refrigerant is at a lower temperature than its surroundings. The most common include ammonia, Freon (and other chlorofluorocarbon refrigerants, aka CFCs), and HFC-134a (a non-toxic hydrofluorocarbon). 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 Here i am talking with respect to vapor compression refrigeration cycle. compression of two-phase mixture from 1-2. Natural gas plants, petroleum refineries, and petrochemical plan­­­­­­­ts and most of the food and beverage processes are some of the industrial plants that utilize vapor compression refrigeration systems. Heat is transferred from the refrigerant to a flow of water. The obtained value of COP of the refrigeration cycle was 4.875. The refrigerant leaves the compressor and enters to the condenser. Since the vapor compression cycle is against the Second Law of Thermodynamics, some work is necessary for the transfer to take place. However, as we have seen in the last example, the back-work-ratio for the Rankine cycle is very small, that is only a small portion of the turbine work is required for the pump. Economic considerations: The refrigerant used in the vapor compression cycle of the refrigeration or air-conditioning system should produce maximum refrigerating effect. The resulting refrigerant vapor returns to the compressor inlet at point 1 to complete the thermodynamic cycle. Evaporation. The easiest way to improve the quality of the feed to the compressor is to make sure that the evaporator completely vaporizes the working fluid. I will keep it in mind, thanks for sharing the information keep updating, looking forward for more posts. If a cylinder of R-22 is moved from a 100F truck body into an 80F shop, the quantity of liquid refrigerant in the cylinder will remain the same. Higher condenser pressure will result in high operating costs. Question: Q No.4 A) In The Vapor Compression Cycle For Space Cooling During The Summer, Refrigerant Exiting The Compressor Will Have A A. 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. Thermal imaging has to be the most advanced and reliable method of identifying liquid line restriction. Question: Q No.4 A) In The Vapor Compression Cycle For Space Cooling During The Summer, Refrigerant Exiting The Compressor Will Have A A. 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. A vapor compression cycle is used in most household refrigerators, refrigerator–freezers and freezers. It could result from algae growth, sedimentation, scale formation or slime. 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. The Vapor Compression Refrigeration Cycle involves four components: compressor, condenser, expansion valve/throttle valve and evaporator. The purpose of a refrigerator is the removal of heat, called the cooling load, from a low-temperature medium. This is the series of articles that describes various important parts of the refrigerators and air-conditioners. Q1. Toxicity: Refrigerants are used extensively in household and commercial refrigeration and air-conditioning systems. Question: When Operating A Refrigerator On The Vapour Compression Cycle The Compressor Operates In The Superheat Region Of The Pressure - Enthalpy Diagram. Which Of The Following Is True? High critical temperature to have large isothermal energy transfer. 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 Compression. It should have high thermal conductivity. Here, compression takes place to raise the temperature and refrigerant pressure. Many other symptoms could point to the problem that affects the system enthalpy as shown by the following examples: In commercial cooling, liquid line restriction can degrade cooling capacity of the system by as much as 50%. The condenser operates at 1.6 MPa and the evaporator operates at 300 kPa. 5. What is its defining feature of these systems? Knowing that the aim of the refrigerator is heat removal and that this process requires work, the COP of the cycle becomes: Some of the Vapor Compression Refrigeration Cycle Problems that may affect this value are: The failure of an industrial refrigeration compressor can be expensive affair to the company and damaging to the manufacturer’s reputation. 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. A vapor compression refrigeration cycle uses R-22 and follows the theoretical single-stage cycle. For the conventional vapor-compression refrigeration system with R404A as the refrigerant, when the evaporating temperature decreases from 0 °C to −25 °C, the pressure ratio of the compressor dramatically increases from 3.8 to 9.2 at the condensing temperature of 50 °C. It condenses and evaporates at temperatures and pressures close to the atmospheric conditions. Vapour Compression Refrigeration Cycle - MCQs with Answers Q1. 34. EXPLANATION :-. The condensing temperature is 48 oC, and the evaporating temperature is -18 oC. The cost of the refrigerant itself should be low enough. Ammonia is slightly flammable and explosive, but its effects can be nullified by taking some precautionary measures. 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. An insight into stratified TES systems, Sustainability Doesn’t Mean Only Reduction in Electricity Consumption but Also in Water Consumption, Five Engineering Applications of Computational Fluid Dynamics, How to Face Challenging Energy Projects: Some Tips for Project Management, Heat Waste for Power Generation: Alternatives to Generate Clean and High-Efficient Energy. Ch 10, Lesson B, Page 2 - The Ideal Vapor-Compression Refrigeration Cycle. 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. Since this process requires work, an electric motor may be used. Here i am talking with respect to vapor compression refrigeration cycle. While some people have viewed this method as environmentally harmful and inefficient, the cycle is still applicable in the industrial sphere. Compressors themselves can be scroll, screw, centrifugal or reciprocating types. Evaporator. 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