A302 HEAT TRANSFER ENHANCEMENT AND DRAG INCREASE IN A CHANNEL WITH A WING-TYPE VORTEX GENERATOR : EFFECT OF PRANDTL NUMBER(Heat Transfer-1)

概要

論文の詳細を見る
The efficiency of heat transfer η, i.e., the ratio between heat transfer enhancement and drag increase from the smooth channel, is discussed for the turbulent and laminar flows in a channel with a wing-type vortex generator (VG) installed on the wall. In this report, the effect of Prandtl number Pr on η is mainly discussed. Various effects on the heat transfer enhancement are investigated by using the results of direct numerical simulation and the energy equations integrally averaged over the whole flow field. η decreases slightly in the turbulent flow with Pr while it increases noticeably in the laminar flow. In the turbulent flow, the temperature fluctuation in the smooth channel is suppressed by the strong thermal diffusion effect at low Pr. The fluctuation promoted by VG becomes effective relatively in such region. In the laminar flow, on the other hand, since there is no background turbulence in the smooth channel, the fluctuation generated by VG directly enhances the heat transfer, which is greater in high Pr region where the thermal diffusion effect is weakened. In addition, the increase of convective heat transfer near the wall has an important effect on the good efficiency for the laminar flow.
2009-11-16