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首页> 外文期刊>Energy Conversion & Management >Free convection heat transfer inside vertical and inclined elliptic tubes with different axis ratio and different inclination and orientation angles
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Free convection heat transfer inside vertical and inclined elliptic tubes with different axis ratio and different inclination and orientation angles

机译：垂直和倾斜椭圆管内具有不同轴比和不同倾斜角和取向角的自由对流传热

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摘要

Experimental investigation of free convection heat transfer from the inside surface of vertical and inclined elliptic tubes of different axis ratios, different orientation angles and different inclination angles with a uniformly heated surface are presented. The axis ratio is changed from 1.5 to 3.5, the inclination angle is changed from 15° to 75° and the orientation angle is changed from 0° to 90°. The experiments covered a range of Rayleigh number, Ra from 6.85 × 10~5 to 1.3 × 10~8. The local and average heat transfer coefficients and Nusselt numbers are estimated for different axis ratios and different orientation angles at different Rayleigh numbers. The experimental results showed that the axis ratio has a significant effect on the local and average heat transfer coefficients. The local Nusselt number (Nu) increases with the increase of axial distance from the lower end of the elliptic tube until a maximum value is reached near the top of the elliptic tube, and then, the Nu gradually decreases. Also, the local Nu increases with the increase of α, φ and AR at the same axial distance. The average Nu increases with the increase of orientation angle, inclination angle and axis ratio (AR) at a constant Ra. Correlations of the average Nusselt number for free convection inside vertical and inclined elliptic tubes with the orientation angles (α), inclination angles (φ) and axis ratios (AR) are presented.
机译：提出了不同轴比，不同取向角和不同倾斜角的垂直和倾斜椭圆管内表面自由对流传热的实验研究。轴比从1.5更改为3.5，倾斜角从15°更改为75°，定向角从0°更改为90°。实验涵盖了瑞利数Ra的范围，从6.85×10〜5到1.3×10〜8。对于不同的轴比和在不同的瑞利数下的不同取向角，估计了局部和平均传热系数以及努塞尔数。实验结果表明，轴比对局部和平均传热系数有显着影响。 Nusselt局部值（Nu）随从椭圆管下端到轴向距离的增加而增加，直到在椭圆管顶部附近达到最大值为止，然后Nu逐渐减小。同样，在相同的轴向距离下，局部Nu随α，φ和AR的增加而增加。在恒定的Ra下，平均Nu随取向角，倾斜角和轴比（AR）的增加而增加。给出了垂直和倾斜椭圆管内自由对流的平均努塞尔数与取向角（α），倾斜角（φ）和轴比（AR）的关系。

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