In recent years various modern improvements have been used to raise the performance of heat systems in various engineering and industrial applications. One of these improvements is the use of porous material. This research focuses on conducting a theoretical study (numerical simulation) via forced convection heat transfer of three channels of various cross-sections (square, rectangular, and triangular) with an equal hydraulic diameter of (0.15 m) with glass spheres filled of a diameter (0.012 m) as a porous martial. The lower surface of the test section is subjected to a uniform heat flux along the fluid flow of (5000 W/m2), while the upper surface is thermally insulated. The type of model used in this study (k- epsilon turbulent model) to simulate and analyze fluid flow inside three channels. This study aims to enhance the thermal properties of the fluid (water) and study its effect on the distribution of temperature, velocity, and pressure, respectively. The results showed that the channel with a triangular cross-section gives the highest distribution of temperature and pressure compared to the rest, and therefore it is considered the optimal design for the channels.