Numerical study on overall thermal performance in SAH duct with compound roughness of V-shaped ribs and dimples

Abstract

: This paper presents the thermal hydraulic performance of a three dimensional rib-roughened solar air heater (SAH) duct with the one principal wall subjected to uniform heat flux. The SAH duct has aspect ratio of 12.0 and the Reynolds number ranges from 2000 to 12000. The roughness has relative rib height of 0.045, ratio of dimple depth to print diameter of 0.5 and rib pitch ratio of 8.0. The flow attack angle is varied from 35°to 70°. Various turbulent flow models are used for the heat transfer and fluid flow analysis and their results are compared with the experimental results for smooth surfaces. The computational fluid dynamics (CFD) results based on the renormalization k-epsilon model are in better outcomes compared with the experimental data. This model is used to calculate heat transfer and fluid flow in SAH duct with the compound roughness of V-shaped ribs and dimples. The overall thermal performance based on equal pumping power is found to be the highest (2.18) for flow attack angle of 55°. The thermo-hydraulic performance for V-pattern shaped ribs combined with dimple ribs is higher than that for dimple rib shape and V-pattern rib shape air duct.

Numerical study of heat transfer enhancement using perforated dual twisted tape inserts in converging‐diverging tubes

“…The mechanism of heat transfer enhancement in case of using TTs is induced swirl flow near the wall that causes higher turbulence in wall area and better fluid mixing. [23][24][25] TTs are cheap and they can be easily installed. TT can be stationary or self-rotating.…”

Experimental study on heat transfer and fluid flow enhancement of a spherical shape obstacle solar air passage

“…The techniques of local heat transfer improvement attract the interests of researchers [5]. Obstacles are often used to improve local heat transfer among the wall and fluid because they cause stream separation and reattachment, consequently resulting in destroying the laminar viscous layer [6][7][8][9][10][11][12]. Bhushan and Singh [8] experimentally investigated the performance of a staggered dimple type roughness SAP.…”

“…The outcome shows that rib-protrusion structure found to be the most efficient structure while rib-dimple structure has only minor advantage than ribbed passage. Kumar and Kim [11] investigated the thermal hydraulic performance of a 3-D obstacles-roughened SAP having W p /H p of 12.0. They found that thermal hydraulic performance for V-pattern shaped obstacles combined with dimpled obstacles is superior as compared with dimpled obstacles shape and V-pattern obstacles shape SAP.…”