Transient Simulation of an Air-source Heat Pump under Cycling of Frosting and Reverse-cycle Defrosting

Abstract

Frost accumulation is a common but undesired phenomenon for air-source heat pump (ASHP) systems in winter operations. Reverse-cycle defrosting that applies heat to the outdoor coil by reversing the thermodynamic cycle, is one of the predominant means for periodic removal of the accumulated frost. This paper presents a dynamic modeling framework for ASHPs under cycling of frosting and reverse-cycle defrosting operations. A uniform model structure was applied to frost formation and melting models, which were incorporated into the evaporator model, without a need for reinitializing the system when the operating mode switches between heating and defrosting. The developed model was simulated to predict transients of a residential ASHP under multiple cycles of frosting and defrosting operations, and results yielded good agreement with measurements.