In the present study, an optimization model is developed for plate-fin heat exchangers (PFHEs) based on the entropy generation minimization method. In the modeling, the entropy generation rate per unit partition plate area, i.e., specific entropy generation rate is proposed as an optimization objective function and the total heat transfer area of a PFHE is considered as a constraint. The model takes into account the irreversibility due to both irreversible heat transfer and pressure drop. The analysis of optimal allocation of total heat transfer area between the hot- and cold-side for a PFHE is conducted with a case study. The results show that optimal geometric parameters of a PFHE such as the fin spacing and fin height on both the hot- and cold-sides can be achieved when the finite total heat transfer area is optimally allocated with minimizing the specific entropy generation rate. In addition, the effects of total heat transfer area, heat transfer rate, as well as the ratio of mass flow rate between the cold- and hot-side fluid on the specific entropy generation rate and optimal allocation ratio of total heat transfer area are also analyzed. (c) 2014 Elsevier Ltd. All rights reserved.