20. Experimental Investigation, Exergy Analysis, and CFD Simulation of Solar Air Heater Roughened with Artificial V-Shaped Ribs on Absorber Surface Artificial Roughness on Absorber Plate

The heat transfer and enhancement of thermal efficiency of a V-shaped rib solar air heater were numerically investigated. Thermal efficiency has been calculated for a solar air heater with absorber surface having artificial roughness in the form of 30° inclined ribs. Two models have been created by taking pitch of inclined ribs as 15 and 20 mm, respectively, on the upper side of absorber surface. Comparison of results for two different rib pitch parameters 15 and 20 mm and heat transfer result. Numerical calculations were performed for various geometrical parameters of the solar duct and focused on the enhancement of maximum heat transfer rate. The maximum value of efficiency is obtained for the model having 15 mm pitch is 43.8% while for the model with 20 mm, pitch is 40.7%. The average value of efficiency is increased to 4.26% for both models when compared with results for smooth absorber surface. The glazing glass cover temperature and temperature of absorber surface are maximum for Model-I at solar intensity 1180–1250 W/m² on the time slot 12:30–1:30 h. The exergy analysis shows that exergy value increases with the increase in solar intensity as the time of day for both models. To validate the results obtained through experiments and to analyze flow phenomena above absorber surface, the CFD analysis is done. The temperature difference obtained is 50 K.