Comparative study on flow and heat transfer characteristics of swirling impingement jet issuing from different nozzles

The flow and heat transfer characteristics of spiral rod (SR), twisted tape (TT), guide vane (GV) and thread grooves (TG) nozzles are compared by numerically and experimentally for swirl angle (theta) = 15-60 and Rey-nolds number (Re) = 6000-12000. An experimental system is built to investigate the heat transfer characteristics of the impingement target. The experimental results show that the TG nozzle has the highest Nusselt number (Nu) in the stagnation region, 19.19% -55.98% higher than that of the other three nozzles for Re = 6000, and SR nozzle has the highest Nu except in the central area. In addition, it is shown that the gas chamber pressure of TG nozzle is much smaller than that of the other three nozzles. The numerical method studies the streamlines, turbulent kinetic energy and vortex distribution in the jet space, and the Nu under different theta and Re of the four types of nozzles, which is verified with the experimental results. The numerical results show that SR nozzle has the largest impingement velocity, the best heat transfer effect, and uniformity, and is obviously influenced by theta. With the increase of the impingement spacing of the four types of nozzles, the impingement area enlarges and cooling effect weakens simultaneously. By studying the flow and heat transfer characteristics, a new swirl nozzle design method based on heat transfer, heat uniformity and pressure loss is established.