Experimental investigation of solar air heater duct with discrete V-rib integrated with staggered elements

This paper presents an experimental investigation of heat transfer and friction factor in a rectangular duct with discrete V-rib integrated with staggered elements. The Reynolds number (Re) of 3000-12,000, ratio of staggered element size to rib height (r/e) of 2-5.5, relative roughness pitch (p/e) of 12, relative roughness height (e/Dh) of 0.045, flow angle of attack (alpha) of 60 degrees, relative gap width (g/e) of 1, relative staggered element position (p'/p) of 0.65 and number of gaps (N-g) of 6. The maximum augmentation in Stanton number is 1.90 times over the smooth duct and maximum thermal efficiency is obtained 86% corresponding to ratio of staggered element size to rib height (r/e) of 3.5.