An Experimental Study of Thermohydraulic Performance of Solar Air Heater Having Multiple Open Trapezoidal Rib Roughnesses
Karmveer KARMVEER, Naveen Kumar Gupta, Tabish Alam, Himanshu Singh
Abstract
In the present experimental study, heat transfer enhancement and friction factor penalty of a solar air heater (SAH) with newly designed artificial roughness attached to the lower side of the absorber plate have been investigated. Multiple open trapezoidal ribs artificial roughness has been designed to take the advantages of secondary flows concerning heat transfer enhancement. Multiple open trapezoidal ribs roughness has been designed considering the following parameters: relative limb length (L/w), angle of attack (α), relative rib height (e/Dh), relative width ratio (W/w), and relative roughness pitch (p/e) having their respective ranges of 0.2–1.0, 0.023–0.054, 6–12, 6, and 60°. The other operating parameter encompassed in the study is the flow Reynolds number, which varied from 2000–16000. The results of the experiment shows that highest augmentation in the Nusselt number (Nu) is observed to be 6.05 times higher with respect to the smooth absorber plate at p/e = 10, L/w = 0.8 and e/Dh = 0.043. In addition, thermohydraulic performance has been evaluated, which is found to be in the range of 3.24–3.79.