Airside heat transfer and friction characteristics for enhanced fin-and-tube heat exchanger with hydrophilic coating under wet conditions

The airside heat transfer and friction characteristics of 14 enhanced fin-and-tube heat exchangers with hydrophilic coating under wet conditions are experimented. The effects of number of tube rows, fin pitch and inlet relative humidity on airside performance are analyzed. The test results show that the influences of the fin pitch and the number of tube rows on the friction characteristic under wet conditions are similar to that under dry surface owing to the existence of the hydrophilic coating. The Colburn j factors decrease as the fin pitch and the number of tube rows increase. For wavy fin, the Colburn j factors increase with the increase of the inlet relative humidity, but for interrupted fin, the Colburn j factors are relatively insensitive to the change of the inlet relative humidity. The friction characteristic is independent of the inlet relative humidity. Based on the test results, heat transfer and friction correlations, in terms of the Colburn j factor and Fanning f factor, are proposed to describe the airside performance of the enhanced fin geometry with hydrophilic coating under wet conditions. For wavy fin, the correlation of the Colburn j factor gives a mean deviation of 7.6%, while the correlation of Fanning f factor shows a mean deviation of 9.1%. For interrupted fin, the correlation of the Colburn j factor gives a mean deviation of 9.7%, while the correlation of Fanning f factor shows a mean deviation of 7.3%.