A novel comprehensive frosting characteristic index jointly considering the refrigerant and configuration of air source heat pumps

Abstract

The refrigerant and configurations represent pivotal elements in the development process of the air source heat pumps (ASHPs), exerting a considerable influence on the formation of frosting. Nevertheless, the refrigerant influence mechanism on the frosting performance remains unclear. To comprehensively quantify the frosting performance for different refrigerants, a detailed theoretical analysis of ASHPs was conducted on the outdoor exchanger heat transfer process. The essential physical parameters of the refrigerant and the configuration that affects the frosting performance of ASHPs were determined. Then, a novel frosting characteristic index (CICOR) was proposed, considering the joint influence of these physical parameters. Moreover, the frosting experiments were conducted using four experimental ASHPs, and the empirical numerical relationships among CICOR, frosting driving force and frosting duration were established. The results indicate that an elevated CICOR value is associated with enhanced frosting suppression capability. The frosting duration can be predicted by calculating the CICOR. With an increase in the CICOR value from 11.26 × 10−2 to 52.68 × 10−2 (s·m5)/kJ2, the frosting duration increased from 21 min to 122 min for ASHPs utilizing R410A. Meanwhile, when the value of CICOR increased from 14.46 × 10−2 to 54.82 × 10−2 (s·m5)/kJ2, the frosting duration increased from 23 min to 69 min for ASHPs using R32.