Abstarct: Due to limited energy resources, increasing energy demand and significant losses in heating systems, it is necessary that providing a solution to reduce energy consumption of these systems. One of the most thermal of systems that used widely in various industries, are shell and tube heat exchangers. In this study, the optimization of shell and tube heat exchangers design is investigated by applying the entransy dissipation theory and genetic algorithm. Entransy is a new physical quantity, has been identified as a basis for optimizing heat transfer processes in terms of the analogy between heat and electrical conduction. Most convective heat transfer processes are characterized by two types of losses, namely: Losses due to fluid friction and those due to heat transfer across a finite temperature difference. Entransy dissipation caused by the irreversibility of the process of heat transfer. Hence, Entransy dissipation is introduced by this two terms as an objective function, and this study are optimized under fixed heat load rate and fixed heat transfer area. The results showed that when heat load rate is fixed, single-objective optimization, can be improved performance of heat exchanger significantly. but single-objective optimization in fixed heat transfer area increase efficiency while pump power increase very much. It is found that the role played by the fluid friction is not fully taken into account when the working fluid of heat exchanger is liquid in single-objective optimization approach. In order to circumvent this problem, a multi-objective optimization approach to heat exchanger design is established.