Thermohydraulic performance augmentation in a solar air heater using a perforated circular segment vortex generator.

Hybrid turbulators have been introduced as a feasible solution to improve heat transfer in fluid channels. In this study, a perforated circular segment was used as a vortex generator to enhance the heat transfer rate in an air collector duct. The effects of key parameters, including Reynolds numbers ranging from 6000 to 18,000 (four values), angles of attack from 30 to 90° (five values), and inline and staggered segment arrangements, on heat transfer, pressure loss, and thermohydraulic performance were investigated. A 3D numerical simulation using the RNG k-ε turbulence model with experimental verification was performed in this study. The results showed that the maximum thermohydraulic performance parameter was 1.3, and an attack angle of 30° provided the best performance. Strong turbulence occurred with an angle of attack of 60°, which caused a large pressure loss in comparison with the heat transfer enhancement. The maximum turbulence kinetic energy shifted from the root to the peak of a segment when the angle of attack increased. The Nusselt number and friction factor of the staggered configuration were 1.72 times and 1.88 times the corresponding values of the inline arrangement.