Heat transfer and exergy analysis of solar air heater tube with helical corrugation and perforated circular disc inserts

Abstract

The effects of perforated circular disc swirl generator on heat transfer (HT) and flow fields in a solar air heater helical corrugated tube have been investigated experimentally. Thermal energy transport coefficient at different values of the corrugation angle (θ), the corrugation pitch ratio (y), the perforation ratio (k), and the perforation disc pitch ratio (s) is studied for Reynolds numbers (Re) ranging from 10,000 to 52,000. Isothermal pressure drop tests and heat transfer experiments under a uniform heat flux conditions have been carried out. The results indicate that in the presence of a perforated circular disc inside the helically corrugated tube, heat transfer is augmented by around 50–60%. Entropy generation in the form of irreversibility is reported. Exergy analysis, in terms of exergy efficiency, is presented. The corrugated tube with swirl generator inserts augments the thermal energy transport coefficient mostly, which is accompanied by a minimum pressure penalty. The combined geometry augments more thermal energy transport coefficient than those of acting alone. A predictive Nusselt number and friction factor correlation are also developed. A large data set has been created for thermal energy transport coefficient and thermal–hydraulic performance, which is beneficial for the design of solar thermal air heaters and heat exchangers.