4. A refrigerant 12 vapour-compression system operates between -10°C and 33°C with saturated liquid on the high side of the expansion valve and saturated vapour entering the compressor whose volumetric efficiency is 88%. An ammonia compression system operates between -35°C and 0°C with saturated liquid entering the expansion valve and saturated vapour entering the compressor whose volumetric efficiency is 85%. The refrigerant -12 evaporator serves as the condenser for ammonia. For the ideal cycle and 10 kW of refrigeration, find a.) the displacement rate of each compressor, and b.) the total actual power required for compression efficiencies of 85 %.

4. A refrigerant 12 vapour-compression system operates between -10°C and 33°C with saturated liquid on the high side of the expansion valve and saturated vapour entering the compressor whose volumetric efficiency is 88%. An ammonia compression system operates between -35°C and 0°C with saturated liquid entering the expansion valve and saturated vapour entering the compressor whose volumetric efficiency is 85%. The refrigerant -12 evaporator serves as the condenser for ammonia. For the ideal cycle and 10 kW of refrigeration, find a.) the displacement rate of each compressor, and b.) the total actual power required for compression efficiencies of 85 %.

Refrigeration and Air Conditioning Technology (MindTap Course List)

8th Edition

ISBN:9781305578296

Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson

Publisher:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson

Chapter28: Special Refrigeration Applications

Section: Chapter Questions

Problem 15RQ: Why is two-stage compression popular for extra-low-temperature refrigeration systems?

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Condensers in these refrigerators are all_______cooled.
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Aa 3. A vapour compression refrigeration system of 2400 kJ/min capacity works at an evaporator temperature of 263 K and a condenser temperature of 303 K. The refrigerant used is R-12 and is subcooled by 6°C before entering the expansion valve and vapour is superheated by 7°C before leaving the evaporator coil. The compression of refrigerant is reversible adiabatic. The refrigeration compressor is two-cylinder, single acting with stroke equal to 1.25 times the bore and runs at 1000 r.p.m. Determine: 1. Refrigerating effect per kg ; 2. Mass of refrigerant circulated per minute; 3. Theoretical piston displacement per minute ; 4. Power required to run the com pressor; 5. Heat removed in through condenser ; and 6. Bore and stroke of the compressor. I want the solution on a piece of paper and using the diagram الأصدقاء المقربون
3. A vapour compression refrigeration system of 2400 kJ/min capacity works at an evaporator temperature of 263 K and a condenser temperature of 303 K. The refrigerant used is R-12 and is subcooled by 6°C before entering the expansion valve and vapour is superheated by 7°C before leaving the evaporator coil. The compression of refrigerant is reversible adiabatic. The refrigeration compressor is two-cylinder, single acting with stroke equal to 1.25 times the bore and runs at 1000 r.p.m. Determine: 1. Refrigerating effect per kg ; 2. Mass of refrigerant circulated per minute ; 3. Theoretical piston displacement per minute; 4. Power required to run the com pressor; 5. Heat removed in through condenser; and 6. Bore and stroke of the compressor.
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A vapour-compression refrigeration system operates with Refrigerant 134 with two evaporators with varying cooling capacity. The low temperature evaporator (#1) operates at -20°C with saturated vapour at its exit and has a refrigeration capacity of 3 tons. The higher temperature evaporator (#2) produces saturated vapour at 3.6 bar at its exit and has a refrigerating capacity of 2 tons. Compression is isentropic to the condenser pressure of 12 bar. There are no pressure drops in the flow through the condenser and the two evaporators and the refrigerant leaves the condenser as saturated liquid at 12 bar. Determine: The mass flow rate of the refrigerant in kg/s through each evaporators;The power input for the compressor, in kW;The coefficient of performance of this refrigeration system;The heat transfer through the condenser in kW;The rates of exergy destruction in each expansion valves in kW for T0 = 300K;Draw the T-s diagram of this system.
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