Thermal and effective assessment of solar thermal air collector with roughened absorber surface: an analytical examination

Abstract

The current work analyses the thermal (η_th) and effective efficiency (${\eta}_{\mathrm{eff}}$) of a solar thermal air collector (STAC) that has an arc-shaped dimple as a roughness geometry on the absorber plate. Nusselt number (Nu) and friction factor (ff) were computed for roughness geometry during the testing, which was done on STAC. Additionally, for different roughness values, the correlations for Nu and ff were developed and further used in this study. The temperature rise parameter and a parametric design are used to assess these efficiencies. The influence of design variables on STAC performance is analyzed using a numerical model based on thermal and effective evaluations. During the investigation, parameters such as relative roughness height (e/D_h) varied from 0.021 to 0.036, relative roughness pitch (p/e) from 10 to 20, arc angle (α) from 45 to 60°, temperature rise parameter from 0.003 to 0.02 and Reynolds number (Re) from 3000 to 48 000 at a constant solar intensity (I = 1000 W/m²). The η_th and ${\eta}_{\mathrm{eff}}$ are observed to be 85% and 78%, respectively, at the optimum values of roughness parameters, i.e. e/D_h = 0.036, p/e = 10, and α = 60°. The curves have been plotted between each of the roughness parameters and Re in order to evaluate the best η_th and ${\eta}_{\mathrm{eff}}$ . The research emphasizes the usefulness of MATLAB for STAC analysis and optimization, roughness parameters of the suggested collector design, by integrating simulation and experimental data.