Experimental investigation and optimization of thermal efficiency of SAHs with V-shaped wire roughness on the absorber

The thermal performance of an explicitly V-shaped wire rough absorber plate solar air heater (SAH) is examined in this work. Our major objective is to raise the convective heat transfer coefficient, therefore improving the thermal efficiency of the SAH. Many tests were carried out to investigate a broad spectrum of characteristics. Among these were the Reynolds number ( Re ), relative roughness height ( e/D h ), rib angles ( α ), pitch to height ratio ( p/e ), and width-to–height ratio (W/H.). The relative roughness height ranged from 0.01 to 0.04; the pitch to height ratio ran from 10 to 40; the Reynolds number fell between 3000 and 8000; and the rib angles ranged from 20° to 90°. The width to height ratio was always 5. Important performance indicators whose examination might give significant insights on the ideal designs for maximizing thermal efficiency are the average friction factor ( f av , average Nusselt number ( Nu av ), and efficiency index ( η ). Especially, it is demonstrated that the maximum efficiency index is reachable under several situations comprising lower Reynolds numbers, lower pitch-to- height ratios, and lower relative roughness heights. The highest efficiency index obtained for a relative roughness height ( e/D h ) of 0.01 and a pitch-to– height ratio ( p/e ) of 40 is 1.36. This implies especially under these specific conditions significant gains in heat transmission efficiency. Applying V-shaped wire roughness shows substantial increases in the Nusselt number and the friction factor compared to a smooth absorber plate. There is optimal thermal performance among different combinations of the studied parameters. For instance, the relative roughness height ( e/D h ) = 0.04 and the pitch-to– height ratio ( p/e ) = 10 recorded the highest Nusselt number of 20.36. These results illustrate how well V-shaped wire roughness may increase SAH efficiency and provide important fresh information for SAH design and optimization as well.