If the throttling valve in Prob. 11-12 is replaced by an isentropic turbine, determine the percentage increase in the COP and in the rate of heat removal from the refrigerated space.

Prob. 11-12

A refrigerator uses refrigerant-134a as the working fluid and operates on an ideal vapor-compression refrigeration cycle between 0.12 and 0.7 MPa. The mass flow rate of the refrigerant is 0.05 kg/s. Show the cycle on a T-s diagram with respect to saturation lines. Determine

(a) the rate of heat removal from the refrigerated space and the power input to the compressor,

(b) the rate of heat rejection to the environment, and

(c) the coefficient of performance.