Performance enhancement of a smooth duct solar air heater incorporating artificial roughness-rectangular ribs with various cutoff corners: A numerical approach

Abstract This study investigates thermal performance improvements in smooth duct solar air heaters (SAHs) using artificial roughness-rectangular ribs (ARRRs) with various cutoff corner (CC) designs. The goal is to optimize the thermal efficiency of SAHs by exploring different CC configurations on the absorber plate's bottom wall, while keeping other surfaces smooth. Four configurations are tested: rectangular (R) with CC = 0.0, type 1 (T1) with CC = l/6, type 2 (T2) with CC = l/3, and type 3 (T3) with CC = l/2. Parameters such as Nusselt number (Nu), thermal enhancement factor (TEF), friction factor (f), entropy generation (Sgen), and Bejan number (Be) are analyzed over a range of Reynolds numbers (Re = 4000 to 18000) and rib pitches (P = 10 to 25). Results show that ribbed SAHs significantly improve heat transfer (HT) over smooth ducts, with the T2 configuration achieving the highest thermal performance (TEF = 1.87) at a smaller rib pitch (P = 10). However, the smooth duct SAH exhibited the lowest friction and entropy generation. This study provides new insights into designing artificial roughness ribs to enhance SAH thermal performance.