The role of heat exchangers has acquired great importance in view of the need to save energy and to have optimal equipment not only in terms of thermal analysis and the economic performance of the installation, but also in terms of other factors such as the energy use of the system and the availability and quantity of energy and raw materials necessary to fulfill a certain function. The main objective of this work is to calculate the effectiveness and the exit temperatures of both the hot and cold fluid of a heat exchanger through an interactive computer program. The interactive computer program developed "InterCal" has been codified in the programming language Matlab 7.0. This language is today a very important tool for professional engineers and scientists. The restriction imposed in the development of the software "InterCal" can be modified by the user, entering the coding of the same...