ABSTRACT

The solar air heater (SAH), which utilizes solar energy to satisfy the building’s heating demands, is an important integrated component of the building. However, SAH’s performance isn’t good enough for it to be used in building. Adding roughness component to the effective zone of heat transfer underneath the absorber plate is the most successful and efficient technique to augment the thermal performance of solar air heater (SAH). In this regards, artificial roughness consisting of several Multiple Open Trapezoidal Rib (MOTR) has been devised with intention of capitalizing on the benefits of secondary flows with regard to the improvement of heat transmission. The geometrical parameters of MOTRs such as relative limb length (L/w = 0.2–1.0), Reynold number (Re = 2000–16000), relative rib height (e/D_h = 0.023–0.054), and relative roughness pitch (p/e = 6–12) have been exploited, while relative width ratio (W/w = 6) and angle of attack (α = 60°) are maintained constant in all the set of experiments. The highest augmentation in Nusselt number (Nu) is observed as 6.07 times as that of smooth absorber plate. In addition, following empirical correlations have been developed for Nu & f with accuracy of average absolute deviation of 5.47% and 5.02%, respectively.

摘要

太阳能空气加热器(SAH)利用太阳能满足建筑物的供暖需求，是建筑物的重要组成部分。然而，SAH 的性能不足以用于建筑。将粗糙度分量添加到吸收板下方的传热有效区域是提高太阳能空气加热器 (SAH) 热性能的最成功和最有效的技术。在这方面，设计了由多个开口梯形肋 (MOTR) 组成的人工粗糙度，旨在利用二次流在改善热传输方面的优势。MOTR 的几何参数，例如相对肢长 (L/w = 0.2–1.0)、雷诺数 (Re = 2000–16000)、相对肋骨高度 (e/D _h = 0.023–0.054)，相对粗糙度间距 (p/e = 6–12) 已被利用，而相对宽度比 (W/w = 6) 和迎角 (α = 60°) 在所有一组实验。观察到努塞尔数 (Nu) 的最高增加量是光滑吸收板的 6.07 倍。此外，针对 Nu 和 f 开发了以下经验相关性，平均绝对偏差的准确度分别为 5.47% 和 5.02%。