A numerical plate-fin heat exchanger (PFHE) model was proposed to investigate the hydrodynamic characteristics of a full-size PFHE by using the porous media approach. Based on the model, effects of the fluid dynamic viscosity and perforated fins on flow distribution and pressure drop of the PFHE were studied. The results showed that flow distribution of the PFHE was improved by increasing the fluid dynamic viscosity or adding perforated fins in each fin channel, but at the cost of an increased pressure drop. Therefore, the relationship between flow distribution and pressure drop was further analyzed under various Reynolds numbers. Based on the results, a correlation among flow distribution, pressure drop, and Reynolds number was derived. Finally, two strategies, the fin channel-based strategy and the header-based strategy were proposed and numerically verified to improve flow distribution of the PFHE. Our results indicate that the first strategy is better than the latter one. (C) 2013 Elsevier Ltd. All rights reserved.