RESUMO

Detailed local Nusselt number distributions in the first pass of a sharp turn two-pass square channel with two configurations of longitudinal vortex generator arranged on one wall were visualized and measured using transient liquid crystal thermography. The corresponding friction factors were measured by pressure transducer probing. The Reynolds number, based on channel hydraulic diameter and bulk mean velocity, was fixed at 1.2 × 10⁴. The vortex generator height-to-hydraulic diameter ratio was 0.12 and three pitch-to-height ratios investigated were 8, 10, and 12. Comparisons in terms of heat transfer augmentation, heat transfer uniformity, and friction loss were performed. The results show that averaged heat transfer enhancement and pressure drop increase with decreasing pitch-to-height ratio for both delta wing and 45 ° V vortex generator arrays. Nevertheless, the pitch-to-height ratio has different effects on the local heat transfer distributions associated with the delta wing and 45 ° V vortex generator arrays because the flow separation bubble occurs behind the 45 ° V vortex generator, but not behind the delta wing vortex generator.