Parametric investigation and correlation development for heat transfer and friction factor in multiple arc dimple roughened solar air duct

Abstract

An experimental investigation was conducted upon a novel multiple arc dimple roughened solar air heater at Sheodeni Ram Ayodhya Prasad College, Bara Chakia, East Champaran, Bihar-845412 under the department of energy sciences This investigation was focused at determining the effect of roughness parameters heat transfer (Nur) and friction (fr) characteristics along with correlation development for Nusselt number and friction factor. The results obtained for roughened duct were compared with non roughened duct on the same condition of flows to examine the improvement of solar air heater heat gain. Nusselt number increased with an increase in Reynolds number whereas friction decreased. Nusselt number and friction factor for roughened duct over smooth duct with varying relative roughness pitch (p/e), relative roughness height (e/Dh), relative roughness width (W/w) and relative arc angle (α/60) were 3.19–5.56, 2.87–5.61, 3.29–5.16 and 2.74–5.18 times for Nur and 1.14–1.62, 1.36–2.27, 1.88 to 2.15 and 1.01–2.16 times for fr respectively. The maximum friction was seen as W/w varied from 4 to 5. On the contrary, Nu decreased in that range. Correlating Nusselt number and friction factor in terms of different parameters were used to derive correlation in terms of p/e, W/w, α/60, e/Dh and flow Reynolds number.