Experimental investigation of frost accretion on microchannel evaporators for household refrigerators

The evaporators used in frost-free refrigerators are inherently susceptible to frost accumulation on their surfaces due to the flow of humid air over a chilled surface. However, the formation of a frost layer compromises the thermal-hydraulic performance of the evaporator by increasing thermal resistance and reducing airflow over time. These impacts depend on both the mass of accumulated frost and its morphology. This study aims to investigate the in-situ performance of a novel microchannel evaporator design for household refrigerators operating under wet conditions. A standardized methodology was developed to induce and evaluate frost formation on the evaporator. Experimental in-situ tests were conducted under various air psychrometric conditions on three selected microchannel evaporator prototypes and a conventional fin-on-tube evaporator to compare the performance degradation of both technologies under different frost morphologies. The results indicated that, despite the promising performance of finned microchannel evaporators under dry conditions, their performance under wet conditions is critical, as clogging appears to occur earlier compared to conventional fin-on-tube technology under the same operating conditions. However, the absence of fins in the initial passes of microchannel evaporators demonstrated strong resistance to frost formation and appears to be a suitable approach for designing frost-resistant evaporators.