An experimental study on the air side heat transfer performance of the perforated fin-tube heat exchangers under the frosting conditions

In this paper, perforated fins were applied to enhance the air side heat transfer performance under frosting conditions for fin-tube heat exchangers with large fin pitches. The frost mass, frost thickness, heat transfer rate and heat transfer coefficient of the perforated fin-tube heat exchangers were measured and analyzed. Although, the frost mass for the perforated fin-tube heat exchangers was 46.7% more than that for the plain fin. The total heat transfer rate and the heat transfer coefficient of the perforated fin was increased by 38.9% and 31.8%. Moreover, under the same heat transfer rate, the heat exchangers with the perforated fins generated less frost mass compared with the plain fin. Two empirical correlations for predicting the j-factor and frost mass of the perforated fin-tube heat exchangers were developed respectively. The correlations were functions of the Reynold number, dimensionless fin pitch, dimensionless temperature, and humidity and Fourier number. The deviations between these predictions and the corresponding measured experimental data fell within ±15.0%.