Enhancement of heat transfer in SAH with polygonal and trapezoidal shape of the rib using CFD

Abstract

A numerical investigation was carried out in Solar Air Heater (SAH) by implementing an artificial rough absorber plate for higher thermal performances. A polygonal transfer rib, the forward and backward trapezoidal rough ribs were nominated for simulation analysis using ANSYS, Fluent version 13.0. The Renormalization k-ε model was selected to predict the augmentation of Nusselt number (Nu), friction factor (ƒ) characterization and Thermo Hydraulic Performances (THP) for a proposed rib by varying relative roughness pitch P/e = [3.33–20] and relative roughness height e/D = [0.03–0.09]. Dittus Boelter and Blasius correlation were used for validating the smooth surface of Nu and ƒ besides compared with the rough surface to ascertain augmentation of heat transfer. The investigation reported on the performance of Nu and ƒ of the proposed rib at a Reynolds number ranges from 3800 to 18,000. The result reveals that the polygonal rib shape with relative roughness pitch P/e = 3.33 has produced higher Nu and gradual reduction of ƒ at Reynolds number 18000. It was found that THP has achieved a maximum of 1.89 in P/e = 10 & e/D = 0.06 at Reynolds number 15000 in the backward trapezoidal rib.