Experimental investigation of solar air heater with new symmetrical GAP ARC GEOMETRY and staggered element

The paper presents experimental analysis of air flowing in solar air heater having new symmetrical gap arc geometry and staggered element. The roughness parameters are arc angle (alpha), relative staggered rib pitch (p'/p), number of gap on half arc (N-g), ratio of gap width to rib height (g/e) and relative staggered rib length (r/e) as 30 degrees, 0.4, 3, 4 and 4, respectively for rib diameter of 2 mm. Reynolds number and relative rib pitch were varied as 3000-15000 and 6-14, respectively. Five rib roughened plates having new symmetrical gap arc geometry and staggered element with relative rib pitch of 6, 8, 10, 12 and 14 were tested. Performance of new symmetrical gap arc geometry and staggered element has been compared with broken arc rib with staggered element and smooth duct. In new symmetrical gap arc geometry and staggered element the maximum increase in friction factor and Nusselt number corresponded to relative rib pitch of 10 and it is 3.88 and 2.18 times as compared to smooth plate. Also new symmetrical gap arc geometry and staggered element has better performance than existing best arc geometry namely broken arc rib with staggered element.