Experimental Investigation for Enhancement of Heat Transfer in Two Pass Solar Air Heater Duct using Multi V-Shaped with Gap Roughness Geometry

The important factors of increasing the efficiency of solar air heater are reducing the heat losses and increasing the heat transfer rate between the absorber plate and working medium air. An experimental work is design and developed to achieve the above goal by providing the double pass instead of single pass in conventional solar air heater. The heat transfer rate is increased by providing the artificial roughness on heat transfer surface. This paper present an experimental study to investigate the effect of roughness and flow parameter on heat transfer using multi v-shape rib with gap geometry. The experimental investigation encompassed the Reynolds number (Re) range from 2000 to 15,000, relative width ratio (W/w) of 3, relative gap distance (Gd/Lv) of 0.24-0.80, relative gap width (g/e) of 0.5-1.5, relative roughness height (e/D) of 0.043, relative roughness pitch (P/e) of 10, angle of attack (α) of 60°. Result is compared to smooth duct under similar flow condition and found that the maximum enhancement is observed at a relative gap distance of 0.69 for relative gap width of 1.0, relative roughness pitch of 10, angle of attack of 60°and relative roughness height of 0.043.