Apex-up discrete-arc rib roughened solar air heater- energy and exergy based experimental study

Abstract

An artificial roughened plate is the most efficient way to disturb the viscous layer and enhance the turbulent intensity near the absorber plate to augment the heat transfer performance of the solar air heater. The present study is carried out by varying the Reynolds number from 3000 to 14000 for novel apex up-flow discrete-arc-rib roughen and smooth absorber plates to examine the exergy-based performance of Sol-Ah. Further, the parameters arc rib angle (α) of 30°, 45° and 60° are investigated with relative gap width (g/e) of 4, relative rib height (e/Dh) of 0.045 and a relative rib pitch (p/e) of 10. The results are compared with recently investigated best exergy-based Sol-Ah systems to justify the superiority of the present roughens plate geometry. It found that exergy destruction due to absorption of irradiance by the absorber (ELA) is 70–80% of total exergy losses. The maximum thermal & exergetic efficiency reported is 82.2 % & 4.14 %, respectively, reported at ΔT/I of 0.0377 m2K/W. The pressure drop increases due to the discrete arc rib absorber plate; nonetheless, this increment is nominal to influence the net useful energy. Additionally, the proposed apex-up discrete arc rib is more effective compared to a smooth plate and previously designed Sol-ah system. Finally, the performance of the present rib roughened Sol-ah is optimized for α = 30°, g/e = 4 and p/e = 10.