Heat transfer of movable air jet impingement over flat plate: experimental implementation

The present study investigates experimentally the influence of a movable air jet impingement on the characteristics of heat transfer over a flat plate. The experiments are conducted with a nozzle translation velocity (V-n) of 200 mm min(-1), a Reynolds number (Re) of 24,000, and a nozzle-to-plate distance ratio (H/D) of 1, 3, 5, and 7. The characteristics of heat transfer on a flat surface due to the use of a movable air nozzle are compared with those of a fixed one using an IR camera. The local Nusselt number (Nu), average Nusselt number ((N) over bar), heat transfer uniformity index (HTU), and heat transfer uniformity (U) are investigated. The results demonstrate that the movable nozzle is more effective than the fixed one for reducing the temperature variation over the heating surface, leading to more heat transfer uniformity. The maximum values of both the Nu and (N) over bar are obtained at a H/D of 1. The U that is improved for the movable nozzle when compared to the fixed nozzle is significantly influenced by the H/D. The maximum values of U are 85 and 72% at a H/D of 7 for the movable and fixed nozzles, respectively. The movable nozzle improves the uniformity of heat transfer more than the fixed one by 75, 42, 39, and 43% at a H/D of 1, 3, 5, and 7, respectively. Moreover, a comparison between the results of the (N) over bar of the present work and those of previous studies is conducted.