Abstarct: In this research, by thermodynamic modeling of a three-stage centrifugal compressor and optimization of its intercooler, the reduction of energy consumption in the multistage compression process is studied. Given the limited energy resources, the increased demand for energy and the considerable losses in thermal systems, providing a solution to reduce energy losses from these systems is essential. One of the most widely used thermal systems, which plays an important role in various industries, is the shell and tubes heat exchangers that can be used as intercoolers in various stages of compression in multi-stage compressors. In the present study, an entransy dissipations theory and genetic algorithm have been used to design an optimal heat exchanger. The purpose of this study is to reduce energy consumption in a three stage centrifugal compressor with an intercooler. In this study, at first part, the performance of intercooler, compressor efficiency, outlet gas temperature of compressor and compression power were investigated. In the second part, using the optimization method of the genetic algorithm, an intercooler was optimized. In the first part of the optimization, entransy dissipations due to the friction and limited temperature difference as a objective function were selected and optimized. Then, in the second part of the optimization, two statements of total entransy dissipations were defined as two objective functions and optimization was performed. In the third section of the optimization, the total cost is selected as a objective function and the intercooler optimized. In the fourth Section of optimization, total cost and efficiency of the intercooler were selected as two objective functions and optimization was performed. In the next step, the effect of optimization of the intercooler on three stage centrifugal compressor was investigated. In this study, the inlet gas into the compressor was assumed ideal gas. From the results of this study, it was observed that for 5 °C increase in inlet Nitrogen temperature of first compressor the outlet Nitrogen temperature will increase 8 to 10 °C., which increased the efficiency of the heat exchanger by about 3%. Optimizing the entransy dissipations caused an increase in the heat transfer rate and efficiency of the heat exchanger by 13% and 18%, respectively. Also, the results showed that by optimizing the entransy dissipations, the isentropic efficiency of the compressor increased to 16%. Also, the results of one part of the study were extracted using the particle swarm optimization method, which was in a good agreement with genetic algorithm method.