Thermohydraulic performance analysis of solar air heater with helical roughness
With the increase in awareness related to the harmful effects of using conventional fuel, the world is accepting the renewable source of energy as the alternative to conventional fuels. The most abundant renewable source of energy is solar energy. It has attracted researchers from time immemorial to work in this field. Harnessing solar energy is an old practice but till today researchers are working on efficient tools or methods to make use of this abundant intermittent solar energy. Solar drying and solar space heating are two such fields where profound research is still going on for finding out the efficient solar air heater, optimizing the design parameters for already existing air heaters and finding correlations to check performance of a solar collectors. Various heat transfer enhancement techniques are used to improve the thermo-hydraulic performance of a solar air heater. Roughness on the absorber plate is one of these techniques of improving the performance of a solar air heater. Augmentation of heat transfer in the solar air heater ducts can be done by breaking the laminar sub layer by employing roughness near the absorber plate. But, this gain is accomplished at the cost of pressure loss in the duct. So research intervention is necessary to model a solar air heater whose increase in thermal performance is more than the decrease in hydraulic performance. In the current study, a numerical simulation on solar air heater with helical roughness is using ANSYS FLUENT 18.0. RNG k-ε turbulence model is used for simulation. The motivation for this study is the formation of eddies near the absorber plate which helps to extract more heat that influences the THPP of a solar air heater. The roughness parameters are optimized by performing simulation by varying relative roughness pitch ratio (P/e) from 3 to 5 for the extent of Reynolds number from 4000 to 15,000.