Impact of fin and hybrid nanofluid on hydraulic-thermal performance and entropy generation in a solar collector using a two-phase approach

Abstract

This research investigates the impact of cylindrical fins and a hybrid nanofluid (HNF) composed of water and copper-zinc oxide on the hydraulic-thermal performance and entropy generation of a solar collector (SC). Numerical simulations are conducted for steady flow utilizing the pressure-based solver. The HNF flow is modeled using the two-phase mixture approach, while the turbulent flow is represented using the standard k-ε turbulence model. The study explores varying inlet Reynolds numbers (Re) from 17,000 to 41,000, volume fractions of nanoparticles (φ) ranging between 1 and 3%, and cylindrical fin heights (λ) of 5, 10, and 15 mm. The results indicate that employing twisted tape in the SC leads to improved thermo-hydraulic performance compared to a SC without twisted tape. Also, the addition of cylindrical fins plays an important role in the flow field because the HNF flow separates after colliding with the fins. This causes the formation of swirling vortices and spatial and temporal fluctuations. The amount of the performance evaluation criterion (PEC) is similar in all cases and decreases with Re. The PEC is much higher than the desired one. Although this trend is decreasing, the results show that in this range of Re, the use of cylindrical fins creates a more reasonable pressure drop (Δp) compared to the enhancement in thermal performance. Finally, the thermal and total entropy generation are reduced and frictional entropy is enhanced by increasing Re. In other words, the increment in the height of the cylindrical fins in the solar system leads to a reduction in the entropy generation.