Thermal Characteristic Optimization of Two-Sided Curvilinear Rib-Roughened Solar Air Heater

Abstract The use of artificial roughness to improve the performance and efficiency of solar air heater is one of the most adopted approaches. The selection of geometrical and flow parameters and their ranges draw the attention of researchers to reach optimum design value. The present experimental and simulation-based investigation deals with the optimization of thermal characteristics (Nusselt number and friction factor) and geometric roughness parameters for a two-sided curvilinear transverse rib-roughened solar air heater. Data collected from the experiment and simulation were further processed by response surface methodology to optimize the thermal characteristics and roughness parameters. The main roughness parameter for two-sided curvilinear rib roughness was the relative roughness height (e/Dh) ranges from 0.7 to 1.4, relative roughness pitch (p/e) ranges from 10 to 25, and Reynolds number (Re) ranges from 3800 to 18,000. Data collected from the simulation are used to develop a mathematical model using the analysis of variance (ANOVA) approach. To adopt the significant value predicted by the model, the coefficient of regression (R2) and confidence interval (p-value and F-value), with a probability of 95%, were considered. Nusselt number and friction factor achieve its optimum value (Nu maximum and f minimum) of 123.84 and 0.012 at e/Dh = 0.031, p/e = 21.42, and Re = 10,900.