Numerical Investigation to Enhance the Thermal Performance of Solar Air Dryers Using Parallelogram Type Transverse Ribs

Present study reports the thermal performance of indirect type solar dryer (ITSD) with numerous roughness profiles through numerical investigation. The artificially roughened parallelogram transverse ribs (ARPTR) are integrated on the absorber plate of ITSD and numerical tests are carried out for various angle of attack ( α = 30–150°), relative roughness pitch ( P/e = 7.14–14.28), relative roughness height ( e/D = 0.021–0.042), and Reynolds number (Re = 3800–18000). The effect of α, P/e , e/D and Re on the thermo-hydraulic performance parameter (THPP), friction factor ( f r ), and Nusselt number (Nu) are analyzed in the present study. The proposed ARPTR exhibits better performance compared to the proposed designs (circular and square roughened ribs) reported in the literature. The pressure drop is found to increase rapidly for the case of P / e = 7, i.e., the rib with larger height; while, the maximum value of pressure is found to decrease gradually with the increase in pitch roughness ( P / e ). The peak value of THPP is found to be 1.79 for e P / e = 14.28, α = 90º, Re = 3800. The higher value of turbulent kinetic energy (TKE) is observed near the bottom of the absorber plate and it decreases in the downstream direction away from the absorber plate. The Peak TKE dissipation occurs between two ribs near the leading edge of the parallelogram ribs. The present design of ITSD with ARPTR exhibits 23.45, and 8.5% higher performance compared to square and circular roughened SAH reported in the literature.