Where _W is the total power consumption of the heat pump system. For the refrigerant side, the capacity is calculated in Equation (3):
Where m_ ref is the refrigerant mass flow rate; href-out is the refrigerant enthalpy at the indoor heat exchanger outlet, and href-in is the refrigerant enthalpy at the indoor heat exchanger inlet. The system cooling and heating COP is defined in Equation (4):
Energy balance between air side and refrigerant side is calculated in Equation (5):