Experimentally validated model of heat pump water heater with a water tank in heating-up transients

This paper presents a linked model to simulate the transient performance of heating-up of a heat pump water heater (HPWH) with a water tank. This linked model consists of a quasi-steady model to simulate the behavior of the vapor compression system and a CFD model that describes the transient flow and temperature fields in the water tank. The interaction between these two models is implemented by the data exchange through the interface between the tank wall and nearby water in the tank. Heat flux profiles of the condenser coils are obtained from the system model and delivered to the water tank CFD model as boundary conditions; CFD model outputs water-side flow and temperature information to the system model for heat transfer calculations. An iterative algorithm is designed to achieve matched solutions of these two models. This linked model is experimentally validated. The results show this model is capable of capturing the dynamic progression of the vapor compression system, as well as the transient fluid dynamics and thermal behavior in the water tank.