General prediction of the thermal hydraulic performance for plate-fin heat exchanger with offset strip fins

The heat transfer and flow friction coefficients for offset strip fins (OSF) used in plate-fin heat exchangers are numerically investigated with well validated 3D models. The effect of the geometrical three-dimensionality is analyzed in a distinctive way to understand the general behavior of the thermal hydraulic performance. Based on the analysis of a large amount of numerical data by CFD techniques for OSF fins, a couple of new correlations for general prediction of the j and f factors are developed, which excellently correlate a variety of geometrical parameters with blockage ratio ranging from 10% to 60%. Moreover, 252 experimental data-points for j and 290 experimental data-points for f covering 24 OSF fins are collected from literatures to examine the predicting abilities of the proposed correlations. The comparisons show that the proposed correlations can present the basic behavior of experimental data with nice accuracy. Further comparisons with the previous correlations from literatures have been done with regards to the same experimental data, which reflect that the proposed ones provide well-adapted predictions for OSF fins with different fin thickness covering a broad range of blockage ratio, while the previous correlations express growing prediction deviations as the blockage ratio increases. On the whole, the proposed correlation predicts 92.5% of the j data and 90.3% of the f data within 20%, with the RMS errors of less than 15%. The present work might be very helpful to guide the optimum design of plate-fin heat exchangers and also evaluate the performance of heat transfer enhancement in the OSF fin channels.