A geothermal vapor compression heat pump maintains the inside air supply of a building at 30 °C and operates with the refrigerant R134a. Underground water is the source of energy for the heat pump and is pumped into the building at 12 °C. The evaporator of the heat pump is designed to operate at a temperature of 8 K below the cold-water inlet temperature. The refrigerant leaves the evaporator as saturated vapor. The condenser operates at 9 bars. The refrigerant leaves the condenser 1.53 K subcoooled. The compressor has an adiabatic efficiency of 72%.
(a) Find the temperature and pressure at each state point of the cycle, in °C and kPa.
(b) Determine the specific work into the compressor, in kJ/kg.
(c) Calculate the specific heat transfer out of the cycle, in kJ/kg.
(d) Obtain the heating coefficient of performance.
(e) Compute the mass rate of cold water required, in kg/min, if the water undergoes a temperature change in the evaporator of 4 K and the heat pump has a capacity unit of 1200 kJ/min.
(f) Sketch the cycle on a T-s diagram. Label all points and processes.