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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 ( Nu ¯ ), 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 Nu ¯ 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 Nu ¯ of the present work and those of previous studies is conducted. [ABSTRACT FROM AUTHOR]

In this study, the cooling of a gas turbine (GT) blade leading edge using a single row of five impinging air jets was numerically and experimentally investigated. The inner surface of the blade leading edge was depicted as a semicircle profile. The numerical study was performed using a shear stress transport (SST) k-ω turbulence model. On the other side, the experimental work was conducted using the infrared (IR) thermal camera. Additionally, the heat transfer characteristics were investigated with changing the Reynolds number (⁠Re ⁠) from 5000 to 40,000. The study was carried out for different cases based on the jet diameter (⁠d ⁠), named as fixed diameter (FD) and variable jet diameter in the streamwise flow direction, i.e., ascending diameter (AD) and descending diameter (DD). The local and average Nusselt numbers and heat transfer uniformity were studied at different operating and design parameters. The results revealed that for FD, increasing the jet diameter decreased the average Nusselt number while it enhanced the heat transfer uniformity. Furthermore, for all values of Re ⁠, the thermal performance of the AD was better than the DD, which has the worst heat transfer uniformity. Finally, predicted developed correlations to estimate the average Nusselt number, surface heat transfer uniformity, and performance evaluation factor (PEF) for all cases of jet diameter were introduced. [ABSTRACT FROM AUTHOR]