Study of solar air heater with discrete arc ribs geometry: Experimental and numerical approach

Abstract

In design of Solar Air Heaters (Sol-AHs) duct, the most efficient way to enhance the heat transfer is by providing artificial roughness on the absorber plate. In the present paper, experimental analyses perform on solar air heater (Sol-AHs) with novel discrete symmetrical arc rib geometry. The studied parameters are ratio of gap width to rib element diameter (g/e) of 2, 3, 4 and 5, ratio of rib diameter height to hydraulic diameter (e/Dh) as 0.045, ratio of rib pitch to rib element diameter as 10, air flow angle of attack as 30°, number of gaps 3 and Re in range of 3000–14000. The performance of novel discrete arc rib solar air heater has been compared with existing staggered V-rib geometry. Maximum enhancement in Nusselt number achieves at g/e equal to 4, which is 3.88 times more compared to the smooth plate, while the highest increment in the thermo-hydraulic performance also observes at g/e of 4. Correlations have been developed for ratio of gap width to rib element diameter and flow parameters. The mathematical model has been developed using a MATLAB code and validates with an experimental study, which further use to design the Solar Air Heater (Sol-AHs) under various operating parameters. Moreover, the new discrete symmetrical arc rib geometry has better performance than the existing best novel V-rib geometry.