Fluid flow and heat transfer in the presence of noncircular obstacles placed in a channel are investigated numerically. Study was performed as three dimensional. Ansys Cfx software was used for numerical study. k–\({\varepsilon}\) model was used for solving of turbulence model equation. Average Nusselt numbers were investigated for six different obstacles (vertical bar, horizontal bar, square, angular square, triangle, and hexagonal) with Reynolds numbers of Re = 10,000, Re = 20,000, and Re = 40,000, and compared with a channel with no obstacle. The largest increase in the average Nusselt number occurred when a vertical bar was placed in the channel. We fitted the average Nusselt number using \({{Nu} = {mRe}^{{n}}{Pr}^{1/3}}\), where n and m are parameters, to achieve \({{Nu} = 0.0285Re^{0.787}{Pr}^{1/3}}\) for all geometries. Drag coefficients were investigated for any obstacle. The velocity profiles and streamlines at the channel output were examined at Re = 20,000 for seven different geometries. The velocity profile along the channel was investigated at Re = 20,000 with a hexagonal obstacle.