With surface ejection or injection occurring at various angles in a rectangular channel, the subject of forced convection heat transfer and fluid flow characteristics is investigated numerically. Thus, the numerical solution of the two-dimensional set of governing differential equations of continuity, momentum, and energy in Cartesian coordinates. At the duct input, it is presumed that the flow will be steady with constant characteristics and uniform velocity and temperature profiles. The Gauss-Siedel iterative method is used to solve algebraic system of equations. Utilizing a bundled "ANSYS" based on the "SIMPLE" technique, computational fluid dynamics is applied. Investigations are conducted into how temperature fields and flow patterns are affected by Reynolds number, injection or ejection angle, mass flow rate, and other variables. The relevant factors in the current study range from 4000 to 120000 for the Reynolds number, from 0.0 to 4 for the blowing ratio, and from 0° to 180° for the injection or ejection angles. The findings demonstrate that under constant injection angles, the blowing ratio increases along with the Nusselt number and friction coefficient ratios. For injection situations at 90° with a Reynolds number, the Nusselt number enhancement is greater. At various injection angle values, a comparison between injection and ejection is made. The generated theoretical results are evaluated against published experimental and experimental data. The comparisons demonstrate good agreement with an average relative error of 4.6%.