You complete a preliminary design of a refrigerator that follows the vapor-compression cycle. Which of the following modifications to the cycle would NOT be expected to lead to an increase in the coefficient of performance of the cycle?

Question

A. Use a turbine instead of the throttling valve to recover energy.
B. Improve the lubrication of the compressor shaft to reduce friction.
C. Use a metal with higher heat transfer capability in the boiler.
D. Move the refrigerator to a location with a lower ambient temperature.
E. Use a regulatable throttling valve instead of a fixed valve.

Answer 1

A. Incorrect. While this would not be a large savings, it would offset a part of the work to the compressor and lower the shaftwork requirement in Equation 5.50. This modification isn’t normally implemented for practical reasons, but in theory it would lead to an increase in the C.O.P. of the cycle.
B. Incorrect. This would increase the efficiency of the compressor and so lower the shaftwork load.
C. Incorrect. This would allow a greater heat removal from the refrigerator compartment and so increase the C.O.P.
D. Incorrect. Lowering the condenser temperature will mean a lower exiting pressure required from the compressor, which means less work.
E. Correct. This will do nothing to change the energy entering and leaving various steps in the cycle.