ABSTRACT

A version improving the efficiency of the Trombe-type assembly is proposed in this study. It consists in equipping the wall with a series of inclined fins forming open cavities of parallelogram section affecting the aerodynamics of the active cavity. The natural convective flow leads to an increase in natural convective heat transfer and improves the overall performance of the assembly. The experimental study is performed with a 0.2 scale assembly. The wall generates a heat flux in a wide range corresponding to the solar radiation while the glass cover is maintained isothermal at cold temperature. The distance between the hot and cold walls compared to the height of the cavity leads to three aspect ratio values (0.1, 0.2 and 0.3). The study performed for a Rayleigh number ranging from 2.81 × 10⁸ to 4.14 × 10⁹ confirms the effectiveness of the new version proposed in this work. With the finned wall, the average natural convective heat transfer increases from 7 to 23% compared to the conventional version without fins, according to the considered configuration. The average Nusselt number is determined for all the tested configurations with a maximum uncertainty of 5%, taking into account the uncertainties of the measured physical parameters. A Nusselt-Rayleigh type correlation is proposed, obtained by means of the least squares optimization method.

摘要

本研究提出了一种提高 Trombe 型组件效率的版本。它包括为墙壁配备一系列倾斜的翅片，形成平行四边形截面的开放空腔，影响活动空腔的空气动力学。自然对流导致自然对流热传递增加并提高组件的整体性能。实验研究是用 0.2 比例的组件进行的。当玻璃盖在低温下保持等温时，墙壁产生与太阳辐射相对应的宽范围的热通量。与空腔高度相比，热壁和冷壁之间的距离导致三个纵横比值（0.1、0.2 和 0.3）。该研究针对范围从 2.81 × 10 ⁸到 4.14 × 10的瑞利数进行^{图 9}证实了这项工作中提出的新版本的有效性。根据考虑的配置，与没有翅片的传统版本相比，翅片墙的平均自然对流传热增加了 7% 到 23%。考虑到测量物理参数的不确定性，为所有测试配置确定平均努塞尔数，最大不确定性为 5%。提出了一种 Nusselt-Rayleigh 型相关性，它是通过最小二乘优化方法获得的。