Role of Artificial Roughness in the Performance Improvement of Solar Air Heaters

Abstract

AbstractSolar radiation is a free, abundant, and clean source of thermal energy. A solar air heater (SAH) is a simple device which acts as a heat exchanger in a way that it extracts thermal energy from the solar radiation. There are various applications in which SAH is used such as space heating and crop drying. As the performance of SAH is low due to less heat transfer coefficient of air which acts as a working fluid in SAHs. Among different techniques, artificial roughness is considered to be the best technique for improving the performance of SAH. Providing roughness element in the direction of flow will help in creating local turbulence which helps in augmenting the heat transfer. Due to increase in turbulence, friction also increases in the flow channel. So, roughness may be provided in such a manner that no significant rise in friction takes place. A lot of roughness geometries were investigated experimentally, numerically to see the impact of roughness elements on heat transfer and friction. The impact of roughness elements on the performance of SAH has been studied for roughness geometry using computational fluid dynamics (CFD). It is a powerful numerical tool which can be utilized to study the flow structure near roughness elements in solar air heaters. This chapter provides the comprehensive information about the different cross-sectional roughness elements, and the effect of these roughness elements on the performance of SAH has also been discussed.KeywordsRoughness elementsSolar air heaterFlow structureCFDHeat transfer