The air-side heat transfer characteristics of flat plate finned-tube heat exchangers were measured and analyzed by varying the fin pitch, number of tube rows, and tube alignment under frosting conditions. Two empirical correlations for predicting the j-factor were developed separately for the inline and the staggered tube alignment, respectively, as a function of the Reynolds number, Fourier number, number of tube rows, and dimensionless hydraulic diameter normalized by fin pitch. The average deviation of the predictions of the present correlations from the measured data was 1.31% for the inline tube alignment and 0.65% for the staggered tube alignment. (C) 2010 Elsevier Ltd. All rights reserved.