An experimental investigation on frosting characteristics and performance of microchannel evaporators with varied aspect ratios

Microchannel evaporators are susceptible to frosting, which can significantly impair heat transfer performance. To provide a basis for microchannel evaporators' effective design and broad application, frosting experiments were conducted in this study. Leveraging infrared thermal imaging and digital image processing technology, the impact of different aspect ratios on refrigerant distribution was quantitatively measured, and the microchannel evaporators' frosting behavior and performance under frosting conditions were analyzed. The results showed that a higher aspect ratio for Evaporator C led to reduced uniformity in the refrigerant distribution, resulting in an increased frost height, a larger frosting coverage area, and greater frost accumulation. Consequently, as frost accumulated, Evaporator C exhibited the most discernible reductions in the heat transfer rate, evaporation pressure, and refrigerant pressure loss, which were 61.07 %, 31.7 %, and 52.83 %, respectively. Therefore, microchannel evaporators with small aspect ratios are recommended where practical field installation conditions permit. And the results are anticipated to provide useful guidance for selecting microchannel evaporators with the optimal aspect ratio, tailored to operate efficiently under frosting conditions.