Computational and experimental performance assessment of rectangular sectioned solar air heater duct provided with new curved ribs

Abstract

AbstractThere are many applications, such as fruits, paddy rice drying, and so on, where air heaters are comprehensively used. The provision of ribs in solar energy‐based air heaters has been accredited to be a beneficial approach for escalating its thermal performance. This investigation reveals the performance evaluation of a rectangular sectioned solar air heater duct placed with the curved type of ribs organized in noncontinuous and truncation patterns. Influence of variation of pitch ratio (4.0–12.0), block‐age ratio (0.06–0.1), the ratio of rib height to the radius of rib curvature (0.75–1), and the ratio of rib truncation gap to its height (0–0.75) at different values of Reynolds's numbers (Re) in the range 12,000–37,000 on the performance revealing factors explicitly heat transfer augmentation factor, the ratio of friction factor, as well as overall thermal performance enhancement (OTPE) have been discussed. The experimentation was performed on a similar rectangular air heater as that of numerical simulation with the same boundary conditions. It is figured out from numerical simulation that the provision of a central truncation gap in the arrangement of ribs helped in the development of vortices with minimal pressure loss due to friction. The greatest Nusselt number augmentation ratio between ribbed and plain plates that was attained is of the order of 2.01 for a pitch ratio of 9.0, blockage ratio of 0.08, the ratio of rib height to the radius of rib curvature 0.25 at the highest value of Re. The obtained friction factor ratio between the ribbed plate and the plain plate is of the order of 2.34 for p/y = 9.0 at maximum Re. The highest value of overall thermal performance enhancement (OTPE) is attained as 1.52 at the pitch ratio of 9, at the maximum value of Re. The central truncation gap of the rib pattern promoted the creation of vortices with a decreased pressure loss penalty. The uppermost value of the factor presenting overall thermal performance enhancement in this work is far superior to unity. This suggests that adding curved ribs to the air heater's duct is a helpful way to improve its overall performance. Empirical correlations have been established between the Nusselt number and geometrical parameters, likewise the friction factor and geometrical parameters using the regression study. The values of the Nusselt number, and friction factor that come from experimental work and developed empirical correlations fall between the highest deviation limits of ±9% and ±8%, respectively. This work is certainly helpful in the context of solar air heaters used for applications such as drying paddy rice.