For the time being, there is a growing endeavor towards supporting energy-saving technologies, most significantly heat exchanger systems, by improving the performance of the heat transfer process. The study model employed is a double-pipe heat exchanger (DPHEX), which is served in an actual project at the Low-Density Polyethylene (LDPE) unit of the State Company for Petrochemical Industries in Basra, Iraq. The prominent goals of this study are to gain a deeper comprehension of the exchanger's performance under advanced operating conditions and to maximize the efficiency of heat transfer between the two fluids in the DPHEX system. The current work applies a distinctive connection of SOLIDWORKS with ANSYS FLUENT software to conduct a simulation design and Computational Fluid Dynamics (CFD) analysis of a heat transfer system in DPHEX. Thermal analysis of exchangers is challenging since many parameters, such as the geometry of the heat exchangers and the varying flow regimes influence the overall heat transfer coefficient. As a result, a Genetic Algorithm (GA) was employed to investigate the optimal design and operating conditions of DPHEX, using a COM server to provide flexible communication between the MATLAB GA toolbox and Aspen HYSYS® software. The preliminary findings from ANSYS FLUENT simulations and GA optimizations demonstrated significant improvements. Specifically, the heat transfer rate rose by 24% and 28%, respectively, also there made up an elevate in the overall heat transfer coefficient to 675 W/m²·K and 751 W/m²·K, correspondingly, from 440 W/m²·K in the as-built heat exchanger. Notably, these results were observed while the outgoing temperature of the chilled ethylene gas was at 49℃, and the efficiency accounted for 87.7%. The study exhibited the feasibility of reducing the cooling water quantity from the traditional mass flow rate of 73,860 kg/hr to 50,400 kg/hr while maintaining a reasonable efficiency of 83% at the LDPE unit. These results were achieved with the leaving temperature of ethylene gas and cooling water set at 50℃ and 34℃, respectively. Hence, minimizing water consumption in heat exchangers brings about environmental, economic, and operational advantages. Generally, the study results have reinforced the importance of simulation tools and their direct contribution to achieving efficient and eco-friendly energy systems.