Experimental Assessment of Thermohydraulic Performance of a Rectangular Solar Air Heater Duct Using Twisted V-Shaped Staggered Ribs

The present experimental effort aims to determine the thermohydraulic performance of a rectangular solar air heater duct with V-shaped ribs staggered over the absorber plate. The performance test is conducted with variable roughness constraints, including relative roughness pitch (P/e) values between 7 and 11, relative staggered distance (d/e) values between 2 and 6, and relative arm length of twisted V-rib (S/e) values between 4.39 and 10.26, and flow Reynolds number values between 3000 and 21,000. The method of liquid crystal thermography is used to observe the dispersion of the Nusselt number over the roughened absorber surface. The maximum Nusselt number and friction factor enhancement ratio for roughened surfaces is determined to be 3.43 and 2.57 times that of a smooth plate, respectively. The parameters of rib configurations are adjusted based on the achieving greatest thermohydraulic performance (THP) index, which corresponds to P/e of 9, d/e of 4, and S/e of 6.15, yielding an optimum thermohydraulic performance measure of 2.69.