Three-dimensional flow characterization of a square array of multiple circular impinging jets using stereoscopic PIV and heat transfer relation

Impinging jets are one of the most industrially essential methods of cooling, for example, the cooling of gas turbine blades and electronic devices, drying or annealing of glasses. Usually, jets are configured for a specific purpose, but the flow tends to be very complicated as each jet interacts with the others, especially near the impingement surface. In the present study, complicated three-dimensional flow from a square array of circular impinging jets was revealed experimentally to investigate the effect on heat transfer characteristics. The flow fiel d was measured by scanning stereoscopic particle image velocimetry to confirm the detailed spatial features of the multiple circular impinging jets as nozzle-to-surface distance and jet-to-jet spacing were changed. Adjacent jets generated vortex rings and roll-up toward the nozzle plate, vortex rings and roll-up sizes changing depending on the experimental parameters. Differences in vorticity and dispersions of velocity from the jets were also observed. The temperature field of the impingement surface was measured using a thermosensitive liquid crystal technique. The spatial distribution of heat transfer coefficient was related to the flow field near the impingement surface.