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The convective heat transfer coefficient in solar air heaters suffers from a reduction due to the formation of a laminar sub-layer between the absorber plate and the air in motion. A viable and efficient strategy to augment the heat transfer coefficient involves introducing artificial roughness in the form of ribs. This study employs numerical simulations to examine the turbulent heat and flow characteristics within a rectangular duct of a solar air heater (SAH) featuring trapezoidal ribs as roughness elements. The governing equations were numerically solved using the finite-volume method and ANSYS FLUENT. The transport equations of turbulent kinetic energy and its dissipation rate were addressed by the RNG k-ε turbulence model. The Nusselt number (Nu), friction factor (f), and thermal performance factor (TPF) were computed across a broad range of conditions, including Reynolds number (6,000≤Re≤18,000), relative roughness height (0.021≤e/Dnd relative roughness pitch (5≤P/e≤20) under constant heat flux conditions. It was determined that the maximum enhancement ratio of Nu was 2.124 times that of a smooth duct when e/Dh=0.043, P/e=20, and Re=6,000. Additionally, the TPF for the SAH featuring trapezoidal ribs attained a peak value of 1.64. [ABSTRACT FROM AUTHOR]