In this article, heat transmission and flow behavior was analyzed in rectangular solar air heater duct. The absorber plate of the solar air heater (SAH) was attached to artificial rough rhombus-shaped ribs with varying rib height (e = 1, 1.25, and 1.4 mm). The finding of this problem was done with a computational exercise in Ansys Fluent R22 by varying dimensionless parameters like Reynolds number (4000–18,000), and relative roughness height (e/Dh), 7.14–10 by keeping constant pitch distance (P = 10 mm), for this study. A two-dimensional domain was taken to investigate, with uniform heat supplied of 1000 W/m2 over an absorber plate made up of aluminum. From various turbulence models, the RNG \(k - \varepsilon\) model with enhanced wall treatment (EWT) was chosen for simulating the fluid flow equations (mass, momentum, and energy). The result showed that the heat transfer coefficient increases (h) with rise in Reynolds number (Re) and found that maximum heat augment and thermal enhancement factor (TEF) at Re = 10,000.