Mathematical models, graphical analysis and numerical solvers allowed us to study heat transfer theory with interesting results. An optimal fin design and optimization process to get an efficient heat exchanger will be presented in this paper. Genetic algorithms technique and finite elements method worked together to find the best geometric configuration for both problems. We designed our own genetic algorithm code named GA7 and adapted it to each optimization problem. Efficiencies below 60% are not economically accepted and must be avoided for fin design. Analysis permitted us to get efficiencies up to 90%. For heat exchanger we could maximize heat flux obtaining different geometric dimension with good results. MatLab® and COMSOL integration increases capacity of GA and offers a new optimization process for COMSOL. This is a great solution for functions of high level of sophistication on energetic systems.