Switch loss of a frost-free refrigerator-freezer with parallel dual-evaporator refrigeration system and its mitigation

The parallel dual-evaporator system has energy-saving potential in frost-free refrigerator-freezers, since it can provide proper evaporating temperature difference for the refrigerator and the freezer, respectively. However, energy loss is generated during the transition period of switches between refrigerating (R-) and freezing (F-) cycles in actual use. In this article, switch loss of a frost-free refrigerator-freezer with parallel dual-evaporator refrigeration system is studied experimentally. Results show that the transition process after F- to R-cycle switch takes 7.17 min and consists of three stages according to R-evaporator’s feeding: short feeding (1.83 min), no feeding (2 min), and continuous feeding (3.34 min). The starvation in R-evaporator during the first two stages leads to switch loss for the refrigerator-freezer, by consuming 23.3% electric energy but yielding only 6.9% capacity for an entire R-cycle. The pump-down (P/D) action before R-cycles accelerates refrigerant’s pumping from F-evaporator and feeding to R-evaporator, thus recovering part of the capacity loss. However, the introduction of P/D is not necessarily energy-efficient because P/D itself consumes considerable electric energy. By contrast, R- to F-cycle switch has little effect on refrigerator-freezer performance due to instant feeding. Dynamic simulation on the transition process will be provided in the future.