Theoretical study on a frost-free household refrigerator-freezer

•A frost-free household refrigerator-freezer is proposed in this paper.•Desiccant is applied to dehumidify the air before it enters evaporator.•Condensation heat of the refrigerant is used to regenerate the desiccant.•The proposed system can achieve high energy efficiency.

This study deals with a frost-free household refrigerator-freezer, in which frosting can be retarded by dehumidifying the air before it enters the evaporator of the refrigerator-freezer via a desiccant-coated heat exchanger. Because the desiccant can be regenerated via the condensation heat of the refrigerant (which is exhausted into ambient air in conventional household refrigerator-freezers), the proposed system can achieve high energy efficiency. Calculations show that the coefficient of performance of this system (COP) is within the range 1.5–2.5 at an ambient temperature of 15–35 °C. Moreover, it is found that the relative humidity of the refrigerator air (RHRA) and the temperature of freezer air (TFA) have a significant effect on COP: COP decreases by about 13% when RHRA varies from 0.4 to 0.8 and by 10% when TFA runs from −18 to −23 °C.