Numerical simulation of a solar air heater equipped with wavy and raccoon-shaped fins: The effect of fins’ height

Abstract

Increasing electricity demand in the world’s energy profile and the focus on carbon footprint reduction motivates countries to utilize renewable sources of energy, such as solar. This has elicited in development of solar air heaters, as a simple solar energy extraction device, academically and practically. Many efforts have been made to upgrade thermally solar air heaters using passive and active remedies. Many types of inserts have been examined; however, the effects of sinusoidal fins are rarely investigated. Therefore, a numerical simulation is implemented to evaluate fins in wavy and raccoon configurations. The effect of fins’ height (25% and 50% of the channel’s height) and the Reynolds number of the turbulent flow (12000 and 24000) are also examined. Normal operating conditions for the inlet air flow is considered. Applying the fins results in better mixing, lower maximum temperature on the absorber plate, and a uniform temperature at the outlet. However, the rise of the friction factor should be considered. The thermal performance factor shows an increment of about 20% through increasing the fins’ height. Increasing the Reynolds number results in a 15% increment in this factor, too. The results positively indicate the promoting role of the wavy and raccoon-shaped fins in solar air heaters and the dominant effect of fin’s height on the thermo-hydraulic performance.