Experimental investigation on performance of a double pass artificial roughened solar air heater duct having roughness elements of the combination of discrete multi V shaped and staggered ribs

Double pass solar air heater (DPSAH) provided with roughness on each side of the absorbing surface is considered as a significant and interesting design advancement that has been used to enhance the performance of the collector. In this paper an experimental analysis has been conducted to study the effect of roughness parameters on thermohydraulic performance of double pass duct having discrete multi V shaped and staggered rib. The study has involved the values of Reynolds number (Re) from 2000 to 20000 and relative staggered rib size (r/e) from 1 to 2.5. Other parameters like relative staggered rib position (P '/P) of 0.2, angle of attack (alpha) of 60 degrees, relative gap distance (G(d)/L-v) of 0.70, relative pitch ratio (p/e) of 10, relative roughness height (e/D) of 0.043 and relative gap width (g/e) of 1.0 are kept constant. Based on the study, heat transfer and pressure drop in single and double pass mode have been estimated at range of ribs and performance parameters and results are compared with smooth ducts under same operating conditions. It has been found that the roughness geometry used on each side of the plate in double pass mode enhances both frictional losses as well as heat dissipation rate. (C) 2016 Elsevier Ltd. All rights reserved.