In the light of introducing new techniques to develop the thermal performance of a solar collector, the development of design represents one of the efficient steps in this field. Using numerical analysis to analyze the flow of fluids and heat transfer refers to the most successful methods for comparison with the experimental findings. In this work, analysis of turbulent forced convection flow and heat transfer in a flat-plate solar water collector equipped with a novel absorber plate under constant heat flux boundary condition is numerically studied. Numerical solutions of the flow domain are implemented by resolving the two-dimensional governing equations of continuity, momentum and energy using finite volume method based on the SIMPLE algorithm technique. The influence of some important parameters such as roughness spacing, relative triangular width and Reynolds number on the local and average Nusselt number, velocity vector distribution and temperature contours has been presented and discussed in detail. Special prominence is given to the grid generation near the triangle sectioned. Results indicate that the heat transfer enhancement is achieved by specific selection of absorber geometry. The present results are determined and compared with the previous experimental data, and the results are very close to each other.