Characteristics and performance evaluation of surface-treated louvered-fin heat exchangers under frosting and wet conditions

Hydrophilic, hydrophobic, and dual (hydrophilic and hydrophobic) coatings were applied to louvered-fins typically used for heat pump heat exchangers, and the characteristics and performance of the heat exchangers under both frosting and wet conditions were compared according to surface treatment. The hydrophilic heat exchanger had the highest air-side pressure drop under frosting conditions. The hydrophobic unit had a lower air-side pressure drop than the others (hydrophilic and dual), due to frost retardation, and the reduction of the heat transfer rate was also smaller. The dual-fin heat exchanger exhibited frost retardation only in the early stage of the experiment, and the heat transfer rate was slightly greater than that of the hydrophilic unit. In wet-condition experiments for evaluating the evaporating performance of surface-treated heat exchangers, the hydrophilic unit had a lower air-side pressure drop than the others, due to the thin film of water condensation on the fins. The differences in the heat transfer rates of the heat exchangers were not significant.