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首页> 外文期刊>International Journal of Heat and Mass Transfer >Convective heat transfer in the channel entrance with a square leading edge under forced flow pulsations
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Convective heat transfer in the channel entrance with a square leading edge under forced flow pulsations

机译：在强制流动脉动下，通道入口的对流传热具有方形前缘

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摘要

Flow characteristics are generally affected by both the regime parameters and channel geometry (cross sectional area, length, converging or diverging parts, bends, obstacles, etc.). Relevant geometric parameters also include the geometry of the channel inlet and entrance length. The present work is an experimental study of convective heat transfer in the entrance region of a plane channel. Steady and pulsating air flow regimes were considered. Heat transfer coefficient was estimated using the method in which the wall was heated and simultaneously its temperature was measured by one and the same electrical circuit. The distributions of heat transfer coefficient were obtained downstream of the square leading edge of the channel. Forced flow pulsations were shown to result in 20% variation of the heat transfer coefficient compared to the corresponding steady flow values, which was observed at the distance of one equivalent diameter from the channel inlet and further downstream. Near the channel inlet (less than one equivalent diameter), deviation of heat transfer from the steady flow values was far more pronounced and non-monotonic in streamwise direction. Local heat transfer enhancement (up to 2.5 times) due to flow pulsations was observed immediately downstream of the channel leading edge. Flow visualization was performed to reveal the mechanisms behind the enhancement. Regular vortices were observed in pulsating flow behind the channel leading edge. At low frequencies of pulsations they promoted mass transfer and hence heat transfer between the core flow and the near-wall region in the channel entrance. The opposite effect was observed at high frequencies. (C) 2018 Elsevier Ltd. All rights reserved.
机译：流动特性通常受状态参数和通道几何形状（横截面积，长度，会聚或发散部分，弯曲，障碍物等）影响。相关的几何参数还包括通道入口和入口长度的几何形状。目前的工作是在平面通道入口区域对流换热的实验研究。考虑了稳定和脉动的气流状态。传热系数是使用加热壁的方法估算的，同时通过一个相同的电路测量壁的温度。在通道的方形前缘的下游获得传热系数的分布。结果表明，与相应的稳定流量值相比，强迫流量脉动导致传热系数发生20％的变化，这是在距通道入口和下游更相等直径的距离处观察到的。在通道入口附近（小于一个等效直径），传热与稳定流量的偏差要明显得多，并且在流向上不是单调的。在通道前缘的下游立即观察到由于流动脉动引起的局部传热增强（高达2.5倍）。进行流程可视化以揭示增强功能背后的机制。在通道前缘后面的脉动流中观察到规则的涡流。在低频脉动下，它们促进了质量传递，从而促进了芯流与通道入口中的近壁区域之间的热传递。在高频下观察到相反的效果。 （C）2018 Elsevier Ltd.保留所有权利。

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