A two-stage cascade vapor-compression refrigeration system uses ammonia in the low- temperature loop ảnd R 12 in the high-temperature loop. The evaporator operates at - 30°C, and the ammonia discharges to the closed cascade condenser at 600 kPa. The R 12 must be 10°Clower than the saturated ammonia temperature to provide adequate cooling. The R 12 compressor has a pressure ratio of 5:1. The ammonia provides 15 tons of cooling. Determine (a) the pressure of the R 12 in the cascade heat exchanger and the condenser; (b) the màss flow rates of ammonia and R 12; (c) the total power, (d) the COP.

A two-stage cascade vapor-compression refrigeration system uses ammonia in the low- temperature loop ảnd R 12 in the high-temperature loop. The evaporator operates at - 30°C, and the ammonia discharges to the closed cascade condenser at 600 kPa. The R 12 must be 10°Clower than the saturated ammonia temperature to provide adequate cooling. The R 12 compressor has a pressure ratio of 5:1. The ammonia provides 15 tons of cooling. Determine (a) the pressure of the R 12 in the cascade heat exchanger and the condenser; (b) the màss flow rates of ammonia and R 12; (c) the total power, (d) the COP.

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

Chapter3: Refrigeration And Refrigerants

Section: Chapter Questions

Problem 12RQ: The condensing pressure is 260 psig and the condenser outlet temperature is 108F for R-22. By how...

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Concept explainers

Entropy

In physics, entropy means the amount of disorder or the degree of randomness associated with a thermodynamic system. The system is not self-organized when the entropy of the system is high. For instance, when a system is at an elevated temperature, its molecules are in random motion, vibrating and colliding with each other. During this scenario, the probability of finding a molecule at a particular place twice, is low. Under this circumstance, the system can be said to be in a high entropy.

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A two-stage cascade vapor-compression refrigeration system uses ammonia in the low-
temperature loop and R 12 in the high-temperature loop. The evaporator operates at
- 30°C, and the ammonia discharges to the closed cascade condenser at 600 kPa. The
R 12 must be 10°Clower than the saturated ammonia temperature to provide adequate
cooling. The R 12 compressor has a pressure ratio of 5:1. The ammonia provides 15
tons of cooling. Determine (a) the pressure of the R 12 in the cascade heat exchanger
and the condenser; (b) the mass flow rates of ammonia and R 12; (c) the total power,
(d) the COP.

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