Theoretical investigation is carried out to determine effect of geometrical parame- ters of V-shaped ribs on heat transfer and fluid flow characteristics of rectangular solar air heater duct with ribbed absorber. Use of artificial roughness in the form of repeated ribs on the absorber plate has found to be a convenient method for the enhancement of heat absorption capacity of the solar collector. The different parameters of artificial roughness are relative roughness pitch ( p/e ), relative roughness height ( e/Dh ), and angle of attack of flow (α) and the range of these parameters has been decided on the basis of practical considerations of the system and operating conditions. Results have also been compared with those of smooth duct under similar flow conditions to determine the enhancement in heat transfer coefficient and friction factor. The maximum enhancement in Stanton number and friction factor is observed to be 1.13 and 1.19 times that of the smooth duct, respectively.