Geometry optimization of double pass solar air heater with helical flow path.

• Geometry of double pass SAH with helical flow path is optimized. • CFD, sensitivity analysis and deferential evaluation optimization are employed. • This work is a continuation of the previous research of the authors. • Thermo-hydraulic performance parameter is increased 16.5% due to optimization. Solar air heaters (SAH) have been widely studied due to their extensive applications in solar energy extraction. This research is in line with the previous study of the authors of this article in which the energy efficiency and heat transfer performance of a double pass solar air heater with helical flow path (HFP) were experimentally and numerically explored in a triangular cross-section channel. Here, the effect of different geometric parameters of this SAH on heat transfer performance is numerically investigated. The optimization procedure was also carried out by the differential evolution (DE). The results of this study were developed by referring to the grid independency and validation of the previous work of the authors. Finally, the effects of triangular section angles and dimensions and the location of the entrance section of each channel were investigated and optimized. The results indicated that optimized geometry resulted in a considerably higher thermo-hydraulic performance as compared with reference geometry for all Reynolds numbers which showed a minimum increment of t 16.5% upon optimization. The inactive vortices produced at the edge of entrance flow passage were reduced in each channel due to optimization which also declined the pressure drop. [ABSTRACT FROM AUTHOR]