Dynamic model of an air-to-water heat pump with R407c as working fluid.
The pressure drops are lumped into two pressure drop (assumed to be quadratic with the mass flow) components in the vapor lines.
The heat exchangers are modeled by a constant heat transfer coefficient on the refrigerant side and a variable heat transfer coefficient (depending on the flow rate) on the secondary fluid side.
The superheating is calculated using a polynomial law of the vapor saturation temperature as a function of the pressure. It is controlled by means of a PI controller.