This paper presents an overview of the concept of second law applications to all processes of thermofluid systems. The presentation is motivated by the need for engineers to be familiar with the new concept of exergy and entropy generation minimization, EGM which are used to design industrial production plants or individual components to maximize their energetic efficiency, and to minimize their environmental impact. It is essential for understanding to what extent resource and energy scarcities, nature’s capacity to assimilate loss as well as the irreversibility of transformation processes, constrain economic action. With these techniques and computational fluid dynamics, CFD, which is used for the conversion of the differential equations of flow to algebraic equations, designers can use the second law to focus on particular regions where design modifications can be made to improve and optimize thermofluid systems performance. Two case studies of exergy/EGM computations are presented for the design of open cycle simple gas turbine and vapour compression refrigeration.