In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to

In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to

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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Similar questions

Welded ______sealed compressors are normally used in household refrigerators.
Why is two-stage compression popular for extra-low-temperature refrigeration systems?
A vapor compression refrigeration cycle undergoes wet compression and maintains the temperatureof the refrigerated space to -25C. The system uses R-12 refrigerant and undergoes isentropicexpansion to the inlet of the evaporator. The compressor discharges the refrigerant at saturatedvapor state at a condensing pressure of 1367 kPa. Determine:a) Determine the enthalpy of all statesb) Determine the quality of refrigerant entering the evaporatorc) Determine the quality of refrigerant leaving the evaporatord) Refrigerant effecte) Work of compressionf) COP If a liquid to suction heat exchanger was installed to prevent wet compression such that it allows 6Csub cooling of refrigerant and superheating to 8C. The expansion of refrigerant is no moreisentropic but isenthalpic. Therefore, determine:g) Enthalpy at different section of the cycleh) COP of the system compared to COP of standard vapor compression cycle.
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
A vapor compression refrigeration systemhas an enthalpy of saturated liquid at the hightemperature side is 341.769 kJ/kg while at lowtemperature side is 131.27 kJ/kg and a latentheat of vaporization of 1312.63 kJ/kg. If themass flow rate of refrigerant is 0.50 kg/s.compute the tons of refrigeration.
A compressor serves two evaporators, one providing 5 tons of cooling at -20 degree F and the other, 10 tons of cooling at 10F. The system is a vapor-compression refrigeration system using R-12 with the condenser pressure at 200 psia. Assume saturated conditions leaving the condenser and evaporators and isentropic compression. Determine (a) the refrigerant flow through each evaporator, (b) the R-12 state entering the compressor, and (c) the compressor power.
A simple vapour compression plant produces (5 tonnes) of refrigeration. The enthalpy values at inlet to compressor, at exit from the compressor, and at exit from the condenser are (183.19, 209.41 and 74.59 kJ/kg) respectively. Determine :- (i) The refrigerant flow rate, (ii) The C.O.P. (iii) The power required to drive the compressor. (iv) The rate of heat rejection to the condenser.
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.
A Freon 12 vapour compression system operating at a condenser temperature of 45Co and an evaporator temperature of 0Co develops 20 tons of refrigeration. Using the p-h diagram for Freon 12, determine; (15) a) The mass flow rate of the refrigerant circulated. b) The heat rejected in the condenser, and c) The Carnot COP and the actual COP of the cycle.
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.
A plant using R134a refrigerant has a cooling capacity of 352 kW of refrigeration. It evaporates at 0 Cand condenses at 35 C, with the 5 of superheat at the evaporator outlet and 5 K of sub-cooling at the condenser outlet. Assuming isentropic compression and ignoring pressure drops in the piping, the evaporator and condenser, determi the following; a) The refrigeration effect b) The mass flow rate of refrigerant ) The compressor power d) The rate of heatrejection at the condenser e) The COP 0 The corresponding Carnot COP g) The percentage Carnot-efficiency
A refrigerant 22 vapor compression system includes a liquid-to-suction heat exchanger in the system. The heat exchanger cools the saturated liquid from the condenser from 32°C to 21°C with vapor which comes from the evaporator at -10°C. The compressor is capable of pumping 20 L/sec of refrigerant. What is the enthalpy of the refrigerant at the suction of the compressor neglecting the heat exchanger? What is the isenthalpic value of the refrigerant in the system neglecting the heat exchanger? What is the refrigerant's enthalpy after compression? What is the COP of the system neglecting the heat exchanger? What is the enthalpy of the refrigerant before it enters in the expansion valve? What is the approximate enthalpy of the refrigerant at the suction of the compressor? What is the estimated enthalpy of the refrigerant after compression? What is the COP of the system? What is the refrigerating capacity of the system in TOR if: a.) without hex and b.) with hex?