Answer Happy

A heat pump using R134a as the working fluid is used to heat a warehouse. The warehouse must be kept at 25°C. A heat duty of 200 kW is required to keep the warehouse at 25°C. The temperature outside on a winter's day is found to be -5°C. The heat pump cycle is shown below: ġH condenser in evaporator OL The following information is known about the working fluid at positions 1, 2, 3, 4, with reference to the heat pump cycle shown above: At position 1: Saturated vapour At position 2: P = 1 MPa, T = 50°C At position 3: Saturated liquid At position 4: P = 100 kPa. The compressor and valve are well insulated. There is no pressure drop in the condenser or evaporator. There are no heat leaks from the condenser or evaporator. Tables of Thermodynamic Properties of R134a are provided. a) Calculate the mass flow rate of the refrigerant (kg/s) b) Determine the temperature (°C) and quality (vapour fraction) of the working fluid at position 4 c) Calculate the work required to run the compressor (kW) d) Calculate the COP of the heat pump e) Calculate the COP of a reversible (Carnot) heat pump operating between the minimum and maximum temperatures of the system, and comment on the reasons for the difference between this and the COP determined in d) f) Discuss three ways to improve the COP of this cycle