A two-stage cascade refrigeration system uses refrigerant-134a as the working fluid and operates between 1.2 MPa and 200 kPa. Each stage operates on an ideal vapour compression refrigeration cycle. Heat rejection from the bottoming cycle to the topping cycle takes place in an adiabatic heat exchanger where it is assumed that both streams enter at 600 kPa. The mass flow rate of the refrigerant through the bottoming cycle is 0.15 kg/s. (a) Draw a labelled schematic of the system and a T-s diagram to describe the cycle (b) Determine the mass flow rate of refrigerant through the topping cycle (c) Determine the rate of heat removal from the refrigerated space (d) Determine the total power input to the compressors (e) Determine the coefficient of performance of the cascade refrigeration system

A two-stage cascade refrigeration system uses refrigerant-134a as the working fluid and operates between 1.2 MPa and 200 kPa. Each stage operates on an ideal vapour compression refrigeration cycle. Heat rejection from the bottoming cycle to the topping cycle takes place in an adiabatic heat exchanger where it is assumed that both streams enter at 600 kPa. The mass flow rate of the refrigerant through the bottoming cycle is 0.15 kg/s. (a) Draw a labelled schematic of the system and a T-s diagram to describe the cycle (b) Determine the mass flow rate of refrigerant through the topping cycle (c) Determine the rate of heat removal from the refrigerated space (d) Determine the total power input to the compressors (e) Determine the coefficient of performance of the cascade refrigeration system

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

Chapter22: Condensers

Section: Chapter Questions

Problem 7RQ: When a standard-efficiency air-cooled condenser is used, the condensing refrigerant will normally be...

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Consider a two-stage cascade refrigeration system operating between the pressure limits of 0.8 and 0.14 MPa. Each stage operates on the ideal vapor-compression refrigeration cycle with refrigerant-134a as the working fluid. Heat rejection from the lower cycle to the upper cycle takes place in an adiabatic counterflow heat exchanger where both streams enter at about 0.4 MPa. If the mass flow rate of the Refrigerant through the upper circle is 0.24 kg/s, determine (a)the mass flow rate of the refrigerant through the lower cycle, (b)the rate of heat removal from the refrigerated space and the power input to the compressor, and (c)the coefficient of performance of this cascade refrigerator. Answers: (a) 0.195 kg/s, (b) 34.2 kW, 7.63 kW, (c) 4.49