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首页> 外文期刊>International Journal of Heat and Mass Transfer >Natural convection heat transfer from two vertically aligned circular cylinders in power-law fluids
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Natural convection heat transfer from two vertically aligned circular cylinders in power-law fluids

机译：幂律流体中两个垂直排列的圆柱体的自然对流传热

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摘要

In this work, laminar natural convection in power-law liquids from a pair of vertically aligned heated cylinders has been studied numerically over the following ranges of conditions: Prandtl number (0.72 ≤ Pr ≤ 10~2), Grashof number (10 ≤ Gr ≤ 10~4), power-law index (0.3 ≤ n≤ 1.5) thereby embracing both shear-thinning and shear-thickening fluid behaviour and the center-to-center gap between the two cylinders was varied over the range (2 ≤ (S/D) ≤ 20). The heat transfer characteristics of the lower cylinder are little influenced by the presence of the upper heated cylinder in line with the previous studies. On the other hand, the average Nusselt number for the upper cylinder could be higher or lower than that of the lower cylinder depending upon the value of (S/D), Grashof number and power-law index. Overall, all else being equal, shear-thinning behaviour can enhance heat transfer by up to 100% whereas shear-thickening has adverse influence on the rate of heat transfer. The present results on Nusselt number and drag coefficient have been correlated using simple analytical forms which permit the estimation of these parameters for the two cylinders in a new application with acceptable levels of accuracy. In addition to the overall heat transfer characteristics, the detailed structure of the velocity and temperature fields is visualised in terms of the streamline and isotherm contours over the preceding ranges of parameters.
机译：在这项工作中，在以下条件范围内，对来自一对垂直排列的加热缸的幂律液体中的层流自然对流进行了数值研究：普朗特数（0.72≤Pr≤10〜2），格拉斯霍夫数（10≤Gr≤ 10〜4），幂律指数（0.3≤n≤1.5）从而同时包含剪切稀化和剪切稠化流体行为，并且两个圆柱体之间的中心距在整个范围内变化（2≤（S / D）≤20）。与先前的研究一致，下部加热缸的传热特性几乎不受上部加热缸的影响。另一方面，取决于（S / D），格拉斯霍夫数和幂律指数的值，上气缸的平均努塞尔数可以高于或低于下气缸的平均努塞尔数。总体而言，在所有其他条件相同的情况下，剪切稀化行为可以将热传递提高多达100％，而剪切浓化对传热速率有不利影响。使用简单的分析形式，可以将当前有关Nusselt数和阻力系数的结果进行关联，从而可以在可接受的精度水平下在新应用中估算两个气缸的这些参数。除了总体的传热特性外，还可以根据先前参数范围内的流线和等温线轮廓来查看速度和温度场的详细结构。

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