A single compressor using ammonia as refrigerant has three evaporators of capacity 30 TR, 20 TR and 10 TR. The temperature in the three evaporators is to be maintained at -10°C, 5°C and 10°C, respectively. The system is provided with individual expansion valve and back pressure valves. The condenser temperature is 40°C. Assume isentropic compression: a. Draw the P-h diagram. b. What is the mass of refrigerant flowing through each evaporator? c. What is the power required to drive the compressor? d. What is the COP of the system?

A single compressor using ammonia as refrigerant has three evaporators of capacity 30 TR, 20 TR and 10 TR. The temperature in the three evaporators is to be maintained at -10°C, 5°C and 10°C, respectively. The system is provided with individual expansion valve and back pressure valves. The condenser temperature is 40°C. Assume isentropic compression: a. Draw the P-h diagram. b. What is the mass of refrigerant flowing through each evaporator? c. What is the power required to drive the compressor? d. What is the COP of the 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

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

Section: Chapter Questions

Problem 9RQ: The approach temperature for the evaporator is A. the difference between the suction and head...

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Problem 3: The high_temperature evaporator (Refrigeration capacity 5 TR) of a multi-evaporator VCR system, working with ammonia, is operating at -6°C and the low temperature evaporator (Refrigeration capacity 10 TR) is operating at -34°C. The condenser pressure is 10.99 bar. The system using individual expansion valves for each evaporator. Assuming saturated conditions at the exit of evaporators and condenser and isentropic compression: a) Find the required power input and COP if a single compressor is used. b) If individual compressors are used for both stage find the power input and COP. c) Compare both cases.
5. A refrigeration system using R-12 as refrigerant consists of throe evaporators of capacities 20 TR at – 5°C, 30 TR at 0°C and 10 TR at 5°C. The vapours leaving the three evaporators are dry and saturated. The system is provided with individual compressors and multiple expansion valves. The condenser temperature is 40°C and the liquid refrigerant leaving the condenser is saturatoed. Assuming isentropic compression in each compressor, find (a) the mass of refrigerant flowing through cach evaporator, (b) the power required to drive the system, and (c) the C.O.P. of the system. [Ans. 27.4 kg/min, 42.25 kg/min: 34.12 kg/min; 38.4 kW; 5.56]