The solar air heater has a relatively lower convection heat transfer coefficient because of development of a laminar sub-layer beneath the absorber plate. The heat transfer coefficient can be improved by interrupting the laminar sub-layer by providing artificial ribs on the flow facing side of the absorber plate. In the present study, a novel type of discrete reverse NACA 0040 profile ribs are used for the performance enhancement of the solar air heater. Various discrete rib parameters such as angle of groove (α, range: 15°–90°), relative gap between the grooves (g/l, range: 0.143–0.333) and relative width of the groove (w/e, range: 0.667–1.667) were optimized for the Reynolds number (Re) range of 6000–18000. Among the various discrete rib parameters, the optimum values were found to be α = 30°, g/l = 0.167 and w/e = 1.333. For this combination, the maximum thermo-hydraulic performance parameter based on the numerical and experimental analysis was found to be 2.65 and 2.578 respectively at the Reynolds number of 6000. The empirical correlations were developed to predict Nusselt number and the friction factor in terms of Re, α/90, g/l and w/e and observed to deviate within ±6% of the corresponding numerical values.

由于在吸收板下方形成层状子层，所以太阳能空气加热器具有相对较低的对流传热系数。通过在吸收板的流向侧上设置人造肋，可以中断层状子层，从而提高传热系数。在本研究中，新型的离散反向NACA 0040轮廓肋用于提高太阳能空气加热器的性能。各种离散的肋条参数，例如凹槽角度（α，范围：15°–90°），凹槽之间的相对间隙（g / l，范围：0.143–0.333）和凹槽的相对宽度（w / e，范围： 0.667–1.667）针对雷诺数（Re）范围为6000–18000进行了优化。在各种离散的肋骨参数中，最佳值为α= 30°，g / l = 0.167和w / e = 1.333。对于这种组合，