Experimental investigation of the performance of microchannel heat exchangers with a new type of fin under wet and frosting conditions

摘要

The performances of three different types of microchannel heat exchangers were experimentally investigated and compared under wet and frosting conditions. In all contrast tests, the heat exchanger with a new type of fin with drainage design exhibited the best performance. Under wet conditions, the capacity of the sample with a new type of fin and that of the sample with a wavy fin were 56.7% and 25.8% higher than that of the sample with a louver fin, whereas the air pressure drops were 63% and 35% lower at 1.0 m-s(-1). Under frosting conditions, the new sample exhibited stable performance, whereas the performance of the wavy fin sample worsened over time because water retention on the heat exchanger increased as the cycles progressed. After 5 frost-defrost cycles, the maximum capacity of the wavy sample decreased by 26%, the air pressure drop increased by 69%, the frosting time decreased by 35%. The new sample was also tested under different frosting conditions to study their effects on frost formation. From the results, the air humidity and evaporator inlet temperature had a significant effect on frosting time and maximum capacity, whereas the air superficial velocity had a small effect on the rate of the frost formation. (C) 2015 Elsevier Ltd. All rights reserved.