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首页> 外文期刊>International Journal of Heat and Fluid Flow >Heat transfer enhancement in a turbulent natural convection boundary layer along a vertical flat plate
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Heat transfer enhancement in a turbulent natural convection boundary layer along a vertical flat plate

机译：沿垂直平板在湍流自然对流边界层中的传热增强

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An experimental study on heat transfer enhancement for a turbulent natural convection boundary layer in air along a vertical flat plate has been performed by inserting a long flat plate in the spanwise direction (simple heat transfer promoter) and short flat plates aligned in the spanwise direction (split heat transfer promoter) with clearances into the near-wall region of the boundary layer. For a simple heat transfer promoter, the heat transfer coefficients increase by a peak value of approximately 37% in the downstream region of the promoter compared with those in the usual turbulent natural convection boundary layer. It is found from flow visualization and simultaneous measurements of the flow and thermal fields with hot- and cold-wires that such increase of heat transfer coefficients is mainly caused by the deflection of flows toward the outer region of the boundary layer and the invasion of low-temperature fluids from the outer region to the near-wall region with large-scale vortex motions riding out the promoter. However, heat transfer coefficients for a split heat transfer promoter exhibit an increase in peak value of approximately 60% in the downstream region of the promoter. Flow visualization and PIV measurements show that such remarkable heat transfer enhancement is attributed to longitudinal vortices generated by flows passing through the clearances of the promoter in addition to large-scale vortex motions riding out the promoter. Consequently, it is concluded that heat transfer enhancement of the turbulent natural convection boundary layer can be substantially achieved in a wide area of the turbulent natural convection boundary layer by employing multiple column split heat transfer promoters. It may be expected that the heat transfer enhancement in excess of approximately 40% can be accomplished by inserting such promoters.
机译：通过沿翼展方向插入一个长平板（简单的传热促进剂）和沿着翼展方向排列成一个短的平板（空气），对沿垂直平板的空气中湍流自然对流边界层的传热增强进行了实验研究（间隙传热促进剂）进入边界层的近壁区域。对于简单的传热促进剂，与常规湍流自然对流边界层相比，在传热剂下游区域的传热系数增加了约37％的峰值。从流动可视化以及同时使用热线和冷线测量流场和热场发现，这种传热系数的增加主要是由于流向边界层外部区域的偏流和低热层的侵入所致。从外部区域到近壁区域的高温流体以大涡旋运动流过促进剂。但是，分流传热促进剂的传热系数在促进剂的下游区域显示出峰值增加约60％。流动的可视化和PIV测量表明，这种显着的传热增强归因于流动通过启动子间隙的流动所产生的纵向涡流，以及从启动子上跳出的大规模旋涡运动。因此，可以得出结论，通过使用多个柱分离式传热促进剂，可以在湍流自然对流边界层的大面积上基本实现湍流自然对流边界层的传热增强。可以预期，通过插入这种促进剂可以实现超过约40％的传热增强。

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