Computational study of combined nozzle jet and spherical promoters for enhanced heat transfer in flat plate solar air collector

This work examines the thermal as well as hydraulic performance (THP) of a flat plate solar air collector (FPSAC), including integrated combined nozzle jets and spherical turbulence promoters, employing computational fluid dynamics (CFD) simulations based on the RNG k−ε turbulence model. The CFD data for the smooth surface duct was validated against existing experimental data and established correlations for smooth surface flat plate collectors, with deviations in Nusselt number and friction factor remaining within acceptable limits, thereby affirming the model reliability. The present study maintained a constant value of sphere-to-hydraulic diameter ratio (DSH/ DH = 0.108), while systematically varying the spanwise pitch ratio (PSPAN/DH = 0.70–1.25), streamwise pitch ratio (PSTREAM/DH = 0.53–0.74), and nozzle diameter ratio (DON/ DIN = 0.38–0.60) over a different Reynolds number (Re) range of 5500–15,500. Geometric configurations such nozzle jet design, spherical promoters arrangement, flow conditions, and fluid characteristics must be studied to enhance FPSAC system performance. Both NuNS/NuSS and THP rise with Re, indicating a considerable influence on turbulence promoter geometry. The best performance was achieved at PSPAN/DH=1.04, PSTREAM/DH=0.60, and DON/DIN=0.45. These findings show that geometric optimization is crucial to efficiency in turbulence flow.