Overview
How can the performance of the given R-134a chiller system be fully evaluated and optimized when its operating parameters (evaporator at 2 bar, condenser at 20 bar, water in at 12 °C and out at 6 °C, ambient 38 °C, flow rate 10 kg/s) yield an actual COP of 3.17 compared with a theoretical Carnot COP of 8.73? In particular, how would you (a) determine the refrigerant mass flow rate and compressor power input from the enthalpy data supplied; (b) calculate and interpret the isentropic efficiency of the compressor; (c) plot and label the cycle on a P-h diagram to illustrate energy transfers; and (d) recommend and justify design or operational changes such as improved heat-exchanger performance, subcooling/superheating control, or alternative refrigerants to narrow the gap between actual and ideal performance? Discuss your reasoning using appropriate thermodynamic principles and equations.