1. A building with an internal temperature of 19C and an outside air temperature of 5C loses heat at a rate of 20kW. To match this heat loss a heat pump operating on a vapour compression cycle is used to extract heat from an external underground heat source. a) b) If the coefficient of performance of the heat-pump system is 2.4 determine the electrical power consumption of the compressor required to drive the heat pump and the rate of heat absorption from the external underground source. [4] c) Sketch the heat-pump system and show the heat pump cycle on a sketch of the pressure-enthalpy diagram identifying the respective processes on the diagrams. [6] d) R134A is to be used as the working fluid in the heat pump. The compressor output pressure and temperature are 7.7bar and 50C and at the condenser outlet the fluid is a saturated liquid. Estimate the mass flow rate of the refrigerant to achieve the required heat output. [5] Why might the time taken for this heat pump to heat up the building from a cold initial condition be slower than for conventional gas central heating? [2]