An ammonia refrigerating system has a load of 250 kW and operates at a condensing pressure of 1400 kPa and an evaporating temperature of -20°C. The refrigerant exits at the evaporator with a 5- degree superheat. The vapor enters the compressor suction at 10-degree superheat. The compressed vapor is discharged from the compressor at the condensing pressure and 150°C. The refrigerant exits the condenser as saturated liquid. a. State the enthalpies at each point: Point enthalpy kJ/kg kJ/kg kJ/kg h2 h3 kJ/kg h4 kJ/kg Answer: kg/sec b. Calculate the mass flow of refrigerant kW Determine the size of the motor drive if the mechanical efficiency of the motor- compressor is 77%. Answer: C. *.. kW Calculate the total heat rejected in the condenser. Answer: d. % Determine the refrigerating efficiency of the system. Answer: е.

An ammonia refrigerating system has a load of 250 kW and operates at a condensing pressure of 1400 kPa and an evaporating temperature of -20°C. The refrigerant exits at the evaporator with a 5- degree superheat. The vapor enters the compressor suction at 10-degree superheat. The compressed vapor is discharged from the compressor at the condensing pressure and 150°C. The refrigerant exits the condenser as saturated liquid. a. State the enthalpies at each point: Point enthalpy kJ/kg kJ/kg kJ/kg h2 h3 kJ/kg h4 kJ/kg Answer: kg/sec b. Calculate the mass flow of refrigerant kW Determine the size of the motor drive if the mechanical efficiency of the motor- compressor is 77%. Answer: C. *.. kW Calculate the total heat rejected in the condenser. Answer: d. % Determine the refrigerating efficiency of the system. Answer: е.

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

Chapter45: Domestic Refrigerators And Freezers

Section: Chapter Questions

Problem 13RQ: Condensers in these refrigerators are all_______cooled.

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Question

An ammonia refrigerating system has a load of 250 kW and operates at a condensing pressure of
1400 kPa and an evaporating temperature of -20°C. The refrigerant exits at the evaporator with a 5-
degree superheat. The vapor enters the compressor suction at 10-degree superheat. The compressed
vapor is discharged from the compressor at the condensing pressure and 150°C. The refrigerant exits
the condenser as saturated liquid.
a. State the enthalpies at each point:
Point
enthalpy
kJ/kg
h
kJ/kg
kJ/kg
h2
kJ/kg
h3
kJ/kg
h4
Answer:
kg/sec
b.
Calculate the mass flow of refrigerant
Answer:
kW
C.
Determine the size of the motor drive if the
mechanical efficiency of the motor-
compressor is 77%.
Answer:
kW
Calculate the total heat rejected in the
condenser.
d.
Determine the refrigerating efficiency of
the system.
Answer:
е.

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