Investigation on Current Control Defrosting Method of Multi-split Variable Refrigerant Flow System

Abstract

There are many indoor units in the multi-split variable refrigerant flow (VRF) system. The continuous operation of heating in winter is longer than that of ordinary household air conditioning, so that the precise defrosting control is energy-saving and improves the comfort for users. In this paper, during the experiment, the indoor temperature was 20℃, the outdoor dry bulb temperature was 7℃, 0℃,-5℃ and-7℃, and the wet bulb temperature was 6℃, 0℃,-6 ℃ and-8℃ respectively. The defrosting temperature, liquid pipe temperature, defrosting time and the current value change rate of the condenser fan were compared when the heating capacity was reduced by 15%. The experiments showed that the current change rate was only related to the frost mass rather than the outdoor temperature. The best fan current change rate was 15%-20% when to defrost for the VRF system. Compared with the traditional defrosting, the phenomenon of thermosensor falling off and the uneven frost formation had little impact on the current control defrosting.