This project inserts itself in improving the understanding of the sensitivity of the dTmin against the parameters that influence it. It is also aimed at helping to improve OSMOSE, a platform designed for the study of energy conversions systems. Three economic criteria have been taken to achieve the heat integration optimization: the net present value, the yearly total cost and the payback period. This paper explores briefly several heat exchanger types and cost estimation models and presents then the program developed on Matlab and Octave for the optimization. The results are discussed, highlighting the fact that the payback period is not relevant for the evaluation of a project, and that the NPV, used by economists, should be considered. Two case studies are presented and compared, when we consider – for a varying heat load – the cold stream with an infinite mcp or the same mcp as the hot stream.