Problem 5 It is well established that the thermal efficiency of a heat engine increases as the temperature TL at which heat is rejected from the heat engine decreases. In a effort to increase the efficiency of a power plant, somebody suggests refrigerating the cooling water before it enters the condenser, where heat rejection takes place. Would you be in favor of this idea? Why? Problem 6 A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -35°C by rejecting waste heat to cooling water that enters the condenser at 19°C at a rate of 0.3 kg/s and leaves at 25°C. The refrigerant enters the condenser at 1.4 MPa and 60°C and leaves at the same pressure subcooled by 10°C. If the compressor consumes 3.2 kW of power, determine (a) the mass flow rate of the refrigerant, (b) the refrigeration load, (c) the COP, and (d) the minimum power input to the compressor for the same refrigeration load.
Problem 5 It is well established that the thermal efficiency of a heat engine increases as the temperature TL at which heat is rejected from the heat engine decreases. In a effort to increase the efficiency of a power plant, somebody suggests refrigerating the cooling water before it enters the condenser, where heat rejection takes place. Would you be in favor of this idea? Why? Problem 6 A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -35°C by rejecting waste heat to cooling water that enters the condenser at 19°C at a rate of 0.3 kg/s and leaves at 25°C. The refrigerant enters the condenser at 1.4 MPa and 60°C and leaves at the same pressure subcooled by 10°C. If the compressor consumes 3.2 kW of power, determine (a) the mass flow rate of the refrigerant, (b) the refrigeration load, (c) the COP, and (d) the minimum power input to the compressor for the same refrigeration load.
Sustainable Energy
2nd Edition
ISBN:9781337551663
Author:DUNLAP, Richard A.
Publisher:DUNLAP, Richard A.
Chapter17: Energy Conservation
Section: Chapter Questions
Problem 7P
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Transcribed Image Text:Problem 5
It is well established that the thermal efficiency of a heat engine increases as the temperature TL at which heat
is rejected from the heat engine decreases. In a effort to increase the efficiency of a power plant, somebody
suggests refrigerating the cooling water before it enters the condenser, where heat rejection takes place.
Would you be in favor of this idea? Why?
Problem 6
A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space
at -35°C by rejecting waste heat to cooling water that enters the condenser at 19°C at a rate of 0.3 kg/s and
leaves at 25°C. The refrigerant enters the condenser at 1.4 MPa and 60°C and leaves at the same pressure
subcooled by 10°C. If the compressor consumes 3.2 kW of power, determine (a) the mass flow rate of the
refrigerant, (b) the refrigeration load, (c) the COP, and (d) the minimum power input to the compressor for
the same refrigeration load.
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