Performance Enhancement of Solar Air Heater with Reverse NACA 0040 Profile Ribs in V-Down Orientation

The primary drawback of the solar air heater (SAH) is a decreased heat transfer coefficient caused by the development of a laminar sublayer on the absorber plate's surface. This laminar sublayer can be eliminated by various methods. One of the methods is to use artificial roughened absorber plate. Artificial roughness will improve the heat transfer coefficient, but it also increases the pressure drop; therefore, the ribs must be provided in such a way that solar air heater's overall thermo-hydraulic performance is enhanced. In the current study, SAH analysis was carried out with smooth and artificially roughened absorber plate in the form of NACA 0040 profile ribs with V-down orientation with an angle of attack of 45° in the reverse manner. Experimental results were used to validate the numerically generated results in the Reynolds number (Re) range of 6000 to 18,000. The values of relative roughness pitch and relative roughness height were kept as 5 and 0.065 respectively. As compared to a smooth absorber plate, the ribs’ provision improved the Nusselt number and friction factor by 37.51–59.42 and 19.89–26.22% respectively. The maximum thermo-hydraulic performance parameter (THPP) was found to be 1.48 at Re of 16,000.