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首页> 外文期刊>International Journal of Heat and Mass Transfer >Experimental investigation on natural convection in horizontal channels with the upper wall at uniform heat flux
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Experimental investigation on natural convection in horizontal channels with the upper wall at uniform heat flux

机译：均热通量的上壁水平通道自然对流实验研究。

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摘要

An experimental investigation on natural convection of air in horizontal channels with well-insulated lower wall and a heated upper wall is carried out. Flow visualization and air temperature measurements are employed to obtain a phenomenological description of air natural convection inside a horizontal, open-ended cavity with a heated upper plate and an unheated lower one. A laminar flow, with a C-loop shape, is observed inside the open-ended cavity. The penetration length is dependent upon the Grashof number. The penetration length increases particularly by increasing either the distance between the walls or the heat flux. The temperature measurements confirm the flow visualization observations. The air temperature profiles inside the open ended cavity indicate that the temperature gradients along the gap cavity are weak for low heat fluxes values. Scale analysis is carried out and shows that penetration length depends on Ra~(1/2), in accordance with other authors. Furthermore, the estimation of the penetration length depends on the values of the thickness of the boundary layer, evaluated in terms of distance between the walls. Monomial correlations for average Nusselt numbers and dimensionless wall temperatures are proposed in a range of Rayleigh number from 2.78 x 10~3 to 3.90 x 10~5 and for an aspect ratio between 2L/b = 10 and 2L/b = 20. The equations agree highly with the experimental results.
机译：进行了下壁和上壁隔热良好的水平通道中空气自然对流的实验研究。使用流动可视化和空气温度测量来获得空气水平对流的现象学描述，该水平对流是在一个水平，开放式空腔内进行的，该空腔具有加热的上板和未加热的下板。在开放式腔体内观察到了C形的层流。穿透长度取决于格拉索夫数。穿透长度特别地通过增加壁之间的距离或热通量而增加。温度测量结果证实了流量可视化观察。开口腔内部的空气温度曲线表明，对于低热通量值，沿间隙腔的温度梯度较弱。根据其他作者的说法，进行了规模分析，结果表明渗透长度取决于Ra〜（1/2）。此外，穿透长度的估计取决于边界壁的厚度值，该边界层的厚度根据壁之间的距离进行评估。在2.78 x 10〜3到3.90 x 10〜5的瑞利数范围内，对于2L / b = 10到2L / b = 20的长宽比，提出了平均Nusselt数和无因次壁温的单项式相关性。与实验结果高度吻合。

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