高Rayleigh数条件下竖圆环夹层内自然对流换热的实验研究

对内壁维持恒热流和外壁向环境冷却的大高宽比竖圆环夹层内自然对流换热进行了实验研究。实验装置高宽比分别为２３５和６６６７，半径比分别为２．０３和３．９２。实验数据整理考虑了热辐射影响以获得对流规律。由于已有工作均未考虑高Ｒａ数区域，首次得到Ｒａ数高达１０￣９的区域内平均Ｎｕ数的换热准则式。在低Ｒａ数区域，亦取得了与前人工作一致的结论。本文结果改进了高Ｒａ数区域换热规律的预测能力。

A EXPERIMENTAL STUDY OF NATURAL CONVECTIVE HEAT TRANSFER OF AIR IN VERTICAL ANNULAR ON THE HIGH RAYLEIGH NUMBER CONDITION

In This Paper, a experimental investigations of natural convection heat transfer of air layers in vertical annuli are presented. In the experiments, the surface of the inner cylinder is maintained at constant heat flax condition while the outer cylinder is cooled in the atmosphere. In order to obtain the convective contribution, overall heat transfer data are corrected for thermal radiation in the annuli. Special emphasis of this investigation is placed on the high Rayleigh number region where no experimental data are available in the literature. Data with Rayleigh number higher than 109 were obtained. the radius ratio studied are 2.03 and 3.92 and the aspect ratio studied are 23.49 and 66.67. Heat transfer correlations for average Nusselt numbers for different Rayleigh number region were developed. For the low Rayleigh number region the results of this paper agree with the correlations reported in literature. Much needed data and correlation in the high Rayleigh number region are obtained for the first time. These results improve the predictive ability for the heat transfer characteristics in the high Rayleigh number region.