Optimization of heat transfer and pressure drop in a solar air heater with ribbed surface

Repeated ribs are used to enhance heat transfer in turbine blades and solar air heaters. The ribs have significant effect on the characteristics of heat transfer and fluid flow. Application of ribs enhances the heat transfer significantly, however simultaneously the pressure drop increases. As a result a balance must be made between the improvement in heat transfer and additional power to overcome the elevated pressure drop. In this study, the effect of ribs on the thermal performance of a flat plate solar air heater is investigated to find the optimum set of parameters in a flat plate solar air heater with ribbed surfaces. Genetic algorithm used to perform the optimization. The optimization carried out to meet two objectives, to attain higher thermal efficiency and to guarantee a practical temperature difference in the inlet and outlet of air flow. In a relatively large range of Reynolds numbers from 2300 to 25000, the fluid flow and heat transfer were evaluated. In order to validate the results, comparison has been made with available data in literature. It was found that the application of ribs improve the thermal efficiency about 10% in low air mass flows, however at higher air flow the additional power due to the pressure drop diminish the effect and even might decrease the efficiency.