Dynamic simulation of air-source heat pump during hot-gas defrost

The dynamic simulation of hot-gas defrost is a challenge and necessary to the simulation of a heat pump. A defrost model that bases itself on the fundamental conservation equations and experimental results is presented in this paper. The distributed model is used here for the details of evaporator and condenser that are important components during the reverse cycle defrost. For validation of the model, a test was set up which contained a nominal 0.88 kW capacity residential air-to-air heat pump that uses a capillary for expansion during the defrost. The good agreement between simulations and experimental results shows that the dynamic defrost model can be used in the research of the heat pump especially for the reverse cycle defrost.