[en] The Computational fluid dynamics (CFD) based analysis is carried out to investigate the thermal and hydraulic performance of circular rib roughened triangular passage Solar air heater (SAH). The circular ribs were provided over the absorber plate. The roughness parameter such as relative roughness pitch (P/e) and relative roughness height (e/D) varies from 4 to 20 and 0.015 to 0.06 (in four sets), respectively, the Reynolds number (Re) varies from 4000 to 18000. The flow governing equations were solved using commercial ANSYS (Fluent) software. The predicted Nusselt number (Nu) and friction factor (f) are validated with the available experimental results. The thermal and hydraulic performance of roughened duct is estimated in the form of Nusselt number and friction factor, respectively. The Thermohydraulic performance parameter (TPP) is also evaluated depending on the friction factor (f) and Nusselt number (Nu) values for SAH. The maximum Thermohydraulic performance parameter (TPP) is observed at Reynolds number of 15000 in case of relative roughness pitch (P/e) and relative roughness height (e/D) value of 12 and 0.06, respectively