Adapting a geared domestic refrigerative dehumidifier for low-temperature operation

• Domestic ungeared and geared dehumidifier operation compared at low-temperatures.
• Methods for pushing geared dehumidifier frosting limit to low temperatures shown.
• Controlling economiser efficiency shows low-temperature operation without frosting.
• Modifying the evaporator also shows low-temperature operation without frosting.
• Geared dehumidifier operation achieved, without frosting, down to 15.4 °C, 70% RH.

It has been established that geared domestic refrigerative dehumidifiers behave poorly when operated in low-temperature household environments where frosting of the evaporator occurs. The hot-side temperature drop introduced by the air-side evaporator economiser is a primary factor in the poor performance of the system if the economiser is too efficient. In this paper, methods for pushing the geared dehumidifier frosting limit to lower ambient temperatures are explored numerically and implemented experimentally with a test system. The methods tested here include a modified refrigerant evaporator, control of the economiser's thermal effectiveness and an integrated approach which includes both methods in conjunction with variable air flow. Results presented in this paper demonstrate operation of a geared domestic dehumidifier with improved dehumidification capacity over the conventional system by around 10% at a moist air condition of 15.4 °C, 70% relative humidity, without evaporator frosting.