Performance enhancement of a solar air heater equipped with flow separators – a CFD approach

Generally, it is found that solar air heaters are associated with lower conversion efficiencies because the heat carrying air medium has lower density. Many investigators have tried different design interventions to improve upon the efficiency of the collectors, especially by adopting different types of turbulence generating mechanisms. Nevertheless, enhancing the thermal effectiveness by means of forming turbulence along the vflow path is possible by using flow separating mechanisms. Flow separating geometries along the flow path such as circular, hexagonal and octagonal channels help in causing the desired turbulence to enhance convective heat transfer. These flow separators facilitate in breaking the viscous sub-layer because of the greater turbulence that they generate. Flow separators also generate a greater exchange of momentum among the air particles carrying heat. This study presents, enhanced convective heat transfer mechanism of the medium created due to the improved turbulence intensity. Circular shaped flow separators are found to provide a significant thermo-hydraulic enhancement factor while the octagonal shaped flow separators are capable of providing a greater thermal performance.