Heat and flow characteristics of air heater ducts provided with turbulators—A review

The use of turbulators in different forms of ribs, baffles, delta winglets, obstacles, vortex generator, rings and perforated blocks/baffles is an effective way to improve the performance of heat exchangers and solar air heaters. Investigators studied the effect of these turbulators for heat transfer and friction characteristics in air ducts. An attempt has been made in this paper to carry out an extensive literature review of turbulators used to investigate heat transfer augmentation and flow structure in air ducts. Based on the review it is found that perforation in ribs/baffles/blocks and combination of combined rib and delta winglet leads to the better thermo-hydraulic performance. The correlations presented by various investigators, in terms of non-dimensional parameters for heat transfer and friction factor in solar air heaters and heat exchangers have also been presented.