Flow and heat transfer characteristics on thermal performance inside the parallel flow channel with alternative ribs based on photovoltaic/thermal (PV/T) system

Highlights: • Heat transfer and flow characteristics were studied for rib cooling modules behind PV panel. • Empirical correlations for Nusselt number and friction factor were proposed for different ribs. • The continuous 60° V-shaped ribs in parallel channel gives the highest thermal performance. • Beyond 13.97% of average output power of PV/T was enhanced with developed cooling modules. • Thermal efficiency of PV/T system was up to about 53.0% with developed cooling modules. The performance of PV/T depends mainly on the temperature on PV panel. In this study, we design multiple cooling modules with installed rib turbulator behind the PV panel. The modules could cool the panel uniformly and improve the performance of the PV/T. Therefore, this leads to the study of flow and heat transfer characteristics in a ribbed parallel channel to evaluate thermal performance based on the photovoltaic/thermal (PV/T) collector. In this work, the four different angle ribs ($\alpha$); 30°, 45°, 60°, and 90°, placed on one sidewall of the parallel channel were studied. The convective fluid was water and the Reynolds number (Re) varied from 400 to 1200. The ratios of the channel aspect ratio (AR), the rib pitch-to-height ratio (p/e), and rib height to hydraulic diameter (e/D_h) were 2.5, 10, and 0.18, respectively. The infrared (IR) thermography camera technique was used to study the heat transfer coefficient distributions on the test surface. The flow fields due to each rib arrangement in a parallel channel were also predicted via numerical simulation. The best rib thermal performance was applied to evaluate the thermal and electrical efficiency of a PV/T collector. The results show that the continuous 45° V-shaped ribs gave the highest thermal performance, while the maximum heat transfer appeared in the case of the continuous 60° V-shaped ribs. The vortex pairs were generated by V-shaped ribs, but the inclined ribs formed the secondary flow. The electrical efficiency of a PV/T system was in the range of 0.8–1.5% when compared to a PV panel. Whereas, the thermal efficiency of the PV/T can up to about 53% and beyond 13.97% for the average output power improved.