This paper presents a numerical investigation of turbulent forced convective f low in a horizontal channel filled with rectangular obstacles located on the lower surface. An exchanger isothermal test plate is embedded in the lower wall, in the fully developed region of the flow. Immediately above this plate, on the upper surface, a black coated isothermally heating resistance facing downwards is installed. This perfectly absorbing surface provides a controlled radiative heat flux on the lower test plate. In this study, custom-built tangential gradient fluxmeters (TGFM) are used to provide local measurements of convective heat transfer so as to validate the numerical predictions. Then, parametric studies are carried out. The profiles for the heat flux densities are presented for different Reynolds numbers in the flow direction along the cold isothermal lower plate. The influence of the presence of an obstacle on the heat flux densities is also investigated. All numerical predictions are carried out with Fluent, previously calibrated against benchmark problems and experimental measurements. In the paper, special emphasis is given in the systematic comparison between experimental and numerical results.