The aim of the study is to investigate the effect of single step rib on the thermal hydraulic performance of rectangular duct solar air heater. In present study single step rib has been used to investigate the thermal hydraulic performance by varying various input parameters such as pitch of rib, angle of attack, and Reynolds number using CFD as a tool. However, CFD results have also been validated with experimental work. A rectangular duct has been designed as per ASHARE standards and experiments are performed for smooth plate and then validated with CFD results. The ratio of Nusselt number for artificially roughened plate to the Nusselt number for smooth plate is also calculated in present study. The maximum ratio is achieved at Re = 15000, for pitch=30 mm and AOA= 15°, which is 3.54. However, the thermal hydraulic performance parameter was reported to be maximum, corresponding to Re = 15000, p = 30 mm and AOA = 15°, which is 2.91.