Combined effect of roughness and suction on heat transfer in a laminar channel flow

摘要

A two-dimensional numerical simulation is carried with the aim to investigate the combined effects of roughness and wall suction on heat transfer performance of a steady-state laminar channel flow. The roughness considered as a square element mounted on the bottom wall of the channel and suction is applied on its walls. Different Reynolds numbers, different suction rates, and various locations of the suction area on the roughness elements are considered. The governing Navier-Stokes equations are solved using open source OpenFOAM software. The results are tested against theoretical results. It is shown that the simple addition of roughness element increases the local Nusselt number in comparison to that without roughness. That increase is further enhanced when localised suction is applied. In addition, it is observed that by applying suction strategically on the roughness, one can reduce the thickness of thermal boundary layer, and remove or at least weaken the vortical motion behind the back-face of element, which in turn leads to an increase in local Nusselt number, demonstrating that suction is an effective means for improving the heat transfer rate in a laminar channel flow. As continuation of study, the effect of space between two elements was investigated and the best space was obtained. It is found that this method is useful to enhance heat transfer performance, especially at high Reynolds numbers.