Experimental and CFD-based thermal performance prediction of solar air heater provided with right-angle triangular rib as artificial roughness

An experimental and two-dimensional computational fluid dynamics (CFD) analysis of a solar air heater has been carried out using right-angle triangular ribs as artificial roughness on the absorber plate as a convenient method for enhancement of thermal performance of solar air heater. The relative roughness pitch (P/e = 7.14-35.71), Reynolds number (Re = 3800-18000), and relative roughness height (e/D = 0.021-0.042) have been selected as design variables for both analysis. ANSYS FLUENT 14.5 with renormalization group k-epsilon turbulence model is selected for the analysis of computational domain of solar air heater during CFD analysis. An enhancement in Nusselt number and friction factor with a decrease in relative roughness pitch (P/e) and increase in relative roughness height are presented and discussed with reference to experimental investigation and CFD analysis. The results of roughened solar air heater duct have been compared with smooth duct under similar flow condition. The optimum value of rib configuration based on constant pumping power requirement has been derived using thermo-hydraulic performance parameter and has been found 2.03 at P/e = 7.14. e/D = 0.042 and at a Reynolds number of 15,000 for the investigated range of parameters.