Complete Derivation of the Moving Boundary Model for an Air Source Heat Pump

The heat pump system is complicated to model dynamically because of the phase changing in both evaporator and condenser. The  moving boundary model tackles this problem by dividing the evaporator and condenser into variable-length zones, and their lengths  vary with the thermal state of the refrigerant. This document explains the full derivation process of the moving boundary model of an air source heat pump system.