A novel coefficient of frosting suppression based on the real-time operating characteristics of air source heat pumps

Abstract

It has been known that for space heating ASHPs, their different configurations and operation may influence their frosting performances. However, there has been no comprehensive coefficient that can be conveniently and comprehensively used to characterize the frosting status, severeness level of frosting, and the potential for frosting suppression during the real-time operation of an ASHP unit. Therefore, in this paper, a novel coefficient of frosting suppression based on the operating characteristic for ASHPs has been proposed, and its development is reported. Firstly, a novel dimensionless coefficient, COFS, to reflect the severeness of frosting for ASHPs was defined. Secondly, an experimental setup with four variable speed experimental ASHP units and test conditions are described. Thirdly, using the experimental results, COFS-based frosting suppression performance maps for the four units were developed. It is shown that because the experimental four units had different frosting suppression abilities, their frosting areas in their frosting maps were 50%, 100%, 94%, and 58%, respectively. In addition, as the test conditions changed, the frosting area on a map area could also change. These have proved that the proposed COFS could effectively reflect the frosting status and the relative level of frosting suppression performances of ASHP in actual operation.