(378h) Thermal Distribution on a Heating FLAT Plated Cooled with a Swirling Impinging Jet

Heat transfer enhancement technology offers numerous benefits to heat exchanger applications. Impinging jet is one of the high potential methods for improving the heat transfer in high flux cooling or heating applications due to their high heat and mass transfer abilities. Most of typical imping jets yield extremely high heat transfer at stagnation points but heat transfer abruptly decreases in radial direction. To cope with the problem, swirling impinging jets (SIJs) were developed to improve the uniformity of heat transfer on impinged plates.

Jet impingement cooling has been applied in various thermal engineering applications because of the efficient removal of locally concentrated heat and easy adjustment of the location where cooling is required. The present work aims to improve heat transfer uniformity by using guide-vanes to induce swirling flow to the jets. The temperature and heat transfer distributions on the impinged plate was visualized using thermochromic liquid crystal (TLC) together with image processing method. Experiments were carried out at different vane numbers of guide-vanes (N) of 4, 5, 6, 7, 8, 9 and 10 and Reynolds numbers (Re_j) of 5000, 10,000, 15,000 and 20,000 (based on the cylinder diameter; D) while the nozzle-to-plate distance ratio (l/D) was kept constant at 1.0. The thermal visualization results show that the heat transfer enhancement of the swirling impinging jet depends on the number of guide-vane (N) and jet Reynolds number (Re_j). The highest impingement heat transfer and the most uniform heat transfer is obtained by using the guide-vanes with N of 10 at Re_jof 20,000. The effect of the number of guide-vanes (N) on the uniformity of thermal distribution is also reported.