This Engineering Master dissertation contributes to the energy efficiency area by applying “Thermal design and optimization” methodologies to evaluate industrial feasible heat exchangers via two case studies. In a first approach, an enhancement to standard castor oil bio-diesel production process was proposed by adding an oil preheater in a place just before pumping the raw material to the transesterification process. A methodology to select this preheater was developed by comparing exergy transfer effectiveness and entropy generation in the usual fluid arrangements for heat exchangers. Due to the best Second Law performance, Shell-&-Tube arrangement was selected and some configurations analyzed by Bell-Delaware method to choose those geometric parameters that perform best. It is to highlight that configuration that has the standard manufacturing recommended geometry relations is in very good agreement with exergy and second law analysis. On the other hand, Plate-&-Frame heat exchangers have their main application in food processing industry when a liquid - liquid situation is required. Due to this, 40 feasible gasketed-plate water-water heat exchangers were simulated to show their behavior, by a performance analysis, using First and Second Thermodynamic Laws indexes on some operational configurations of them. Operational variable parameters were heat exchanger area, cold fluid port connection allocation and room temperature. Main conclusion is that counter-current configurations have better performance than parallel flow configurations due to influence of finite temperature difference. Additionally, room temperature difference is a parameter that must be taken into account to select this kind of heat exchanger.