
(a)
The actual coefficient of performance of the refrigerator.
(a)

Answer to Problem 108P
The actual coefficient of performance of the refrigerator is
Explanation of Solution
Write the formula to calculate the mass flow rate of a refrigerant
Here, volume flow rate at inlet 1 is
Write the formula to calculate the power consumption of the compressor
Write the formula to calculate the refrigeration load
Here, heating load rate is
Write the formula to calculate the actual coefficient of performance.
Conclusion:
Refer Table A-12, “Saturated refrigerant-134a: Pressure table”, obtain the properties of refrigerant R-134a at initial pressure
Refer Table A-13, “Superheated refrigerant-134a”, obtain the properties of refrigerant R-134a at exit pressure
Substitute
Substitute
Substitute
Substitute
Thus, the actual coefficient of performance of the refrigerator is
(b)
The maximum coefficient of performance of a reversible refrigerator.
(b)

Answer to Problem 108P
The maximum coefficient of performance of a reversible refrigerator is
Explanation of Solution
Write the formula to calculate the maximum coefficient of performance of a reversible refrigerator.
Here, absolute temperature of high and low temperature reservoir is
Conclusion:
Convert the unit of temperature
Convert the unit of temperature
Substitute 296 K for
Thus, the maximum coefficient of performance of a reversible refrigerator is
(c)
The minimum volume flow rate at the compressor inlet.
(c)

Answer to Problem 108P
The minimum volume flow rate at the compressor inlet is
Explanation of Solution
Write the formula to calculate the minimum power input to the condenser for the same refrigeration load
Write the formula to calculate the minimum mass flow rate
Write the formula to calculate the minimum volume flow rate at the compressor inlet.
Conclusion:
Substitute 26.91 for
Substitute
Substitute
Thus, the minimum volume flow rate at the compressor inlet is
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Chapter 6 Solutions
Thermodynamics: An Engineering Approach
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