Question

6. An office building requires a heat transfer rate of 20 kW to maintain the inside temperature at 21°C when the outside temperature is 0°C. A vapor-compression heat pump with Refrigerant 134a as the working fluid is to be used to provide the necessary heating. The compressor operates adiabatically with an isentropic efficiency of 82%. Specify appropriate evaporator and condenser pressures of a cycle for this purpose assuming Δ1cond-Al evap-10°C, as shown below. The states are numbered as shown below. The refrigerant exits the evaporator as saturated vapor and exits the condenser as saturated liquid at the respective pressures. Determine the a.) evaporator and compressor pressures, as specified above; b.) mass flow rate of refrigerant, in kg/s; C.) comnpressor power, in kW; d.) coefficient of performance and compare with the coefficient of performance for a Carnot heat pump cycle operating between reservoirs at the inside and outside temperatures, respectively. e.) Thought question: What would happen if the compressor had a leak, and its outlet pressure were lower than your specified value in part a.)? 2 2s AT cond 21°C 0°C 4 AT evap

Answer 1

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