Heat transfer interactions between skin-type condensers and evaporators and their effect on the energy consumption of dual-skin chest-freezers

Abstract

A theoretical and experimental study was carried out aiming at the effect of the interaction between a skin condenser and a skin evaporator on the energy consumption of a chest-freezer for household applications. The refrigeration system was modelled assuming that the insulation has a constant temperature at the central plane midway both heat exchangers. Concurrently, a chest-freezer was instrumented with thermocouples, a mass flow meter, and pressure and power transducers. Energy consumption tests were conducted in a climate chamber for surrounding air temperatures of 16, 25, 32 and 43 °C. The effect of the heat exchangers on the compressor run-time ratio was analyzed by changing the thermostat setting so that six different cabinet air temperatures were achieved for each ambient temperature. The energy consumption predictions were compared against the experimental counterparts, showing deviations within a ±10% error band. The theoretical analysis showed that the thermal load increased by 11% due to the interaction between the heat exchangers. The simulations revealed that, for the surrounding air temperature of 32 °C and freezer temperature of −18 °C, the evaporator and condenser lengths could be reduced by 46 and 70%, respectively, and the overall energy consumption decreased by 7% if the tube pitch of both heat exchangers was modified and the original plastic tape replaced by an aluminum one. Furthermore, increasing the insulation thickness from 86 to 100 mm reduced the contribution of the thermal bridge between the heat exchangers to the thermal load to 1.5% only.