Numerical model for liquid-to-liquid heat pumps implementing switching mode

Abstract

Residential reversible liquid-to-liquid heat pump systems are effective systems to increase energy efficiency and decrease gas emissions of buildings that can supply both the cooling and heating demand of a building due to the reversible capability. This document presents an innovative model developed in Matlab/Simulink that simulates the dynamic behavior of liquid-to-liquid heat pump systems. It is based on a physics-based numerical model capable to switch the refrigerant flow direction and the behavior of the PHEX (condenser or evaporator) according to the actual working mode. With this model, an analysis of the transient states during the switch of the operation mode is carried out. The model was validated with experimental tests for both the heating and the cooling modes separately. For each working mode test, a sudden change in the working conditions of the system was forced to trigger a fast transient state. Then, the validated model was used to carry out a simulation of a switching mode, starting in the cooling mode and finishing in the heating mode