A food storage locker requires a refrigeration system of 2,400 kJ/min capacity at an evaporator temperature of -10OC and a condenser temperature of 30OC. The refrigerant used is freon-12 and sub-cooled by 6OC before entering the expansion valve and vapor is superheated by 7OC before leaving the evaporator coil. The compression of refrigerant is isentropic. The refrigeration compressor is two-cylinder, single-acting with stroke equal to 1.25 times the bore diameter and operates at 1000 rpm. Determine: (a) refrigerating effect, (b) mass of refrigerant to be circulated, (c) theoretical piston displacement per minute

A food storage locker requires a refrigeration system of 2,400 kJ/min capacity at an evaporator temperature of -10OC and a condenser temperature of 30OC. The refrigerant used is freon-12 and sub-cooled by 6OC before entering the expansion valve and vapor is superheated by 7OC before leaving the evaporator coil. The compression of refrigerant is isentropic. The refrigeration compressor is two-cylinder, single-acting with stroke equal to 1.25 times the bore diameter and operates at 1000 rpm. Determine: (a) refrigerating effect, (b) mass of refrigerant to be circulated, (c) theoretical piston displacement per minute

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

Chapter47: High-pressure, Low-pressure, And Absorption Chilled-water Systems

Section: Chapter Questions

Problem 13RQ: The subcooling temperature in a condenser can be measured by taking the difference between the A....

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Q1.2 Consider a two-stage compression refrigeration system operating between the pressure limits of 0.8and0.14 MPa(see Fig. Q 2). The working fluid isrefrigerant -134a. The refrigerant leaves thecondenser as a saturated liquid and is throttled to aflash chamberoperating at0.4 MPa. Part ofthe refrigerant evaporates during this flashing process, and this vapour is mixed with the refrigerantleaving the low-pressure compressor. The mixture is then compressed to the condenser pressure bythe high-pressure compressor. The liquid in the flash chamber is throttled to the evaporator pressure,and it cools the refrigerated space as it vaporizes in the evaporator. Assuming the refrigerant leavesthe evaporator as saturated vapor and both compressors are isentropic, determine(a) the coefficient of performance (COP).Re-draw the schematic diagram and sketch the cycle accurately on a T-s diagram with the propertyvalues labelled at all state points.