On the thermo-flow behavior in a rectangular channel with skewed circular ribs

¹ Department of Mechanical Engineering, Urmia University, Urmia, Iran
² School of Mechanical Engineering, University of Tabriz, Tabriz, Iran

^a Corresponding author : khodayari.b@gmail.com

Received: 4 July 2016
Accepted: 13 September 2016

Abstract

The enhancement of heat transfer by the turbulator ribs in cooling channels causes increases of pressure drop. To achieve high thermal performance, a variety of techniques are employed. This study numerically investigates the heat transfer, fluid flow and thermal performance factor in the rib-roughened straight rectangular channel. The ribs have a circular shape and are mounted on the two opposite walls in a staggered arrangement. Four different rib attack angles of 90°, 60°, 45° and 30° to the main flow direction are treated. The results are obtained at entrance Reynolds number of range 25 000–50 000. Air is considered as convective fluid in steady state distribution. The three-dimensional flow is simulated with a two-layer k-ε turbulence model. The governing equations are solved by a control-volume based procedure using second-order upwind scheme. The computational results are compared with the experimental data under the same conditions. It is found that regarding heat transfer enhancement, circular ribs are in preference to block ones. In addition, the angled ribs could enhance the heat transfer significantly when compared to the ribs in 90° due to the generation of secondary flows. Concerning thermal performance factor, the optimum rib angle is also proposed for different Reynolds numbers.