Air jet impingement heat transfer at low nozzle-plate spacings
Air jet impingement heat transfer at low nozzle-plate spacings
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DOI：
10.1016/0017-9310(94)90059-0
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发表时间：
1994-08
影响因子：
5.2
通讯作者：
D. Lytle;B. W. Webb
中科院分区：
文献类型：
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作者：
D. Lytle;B. W. Webb
采用红外热成像技术对小于一个喷嘴直径的空气射流冲击局部换热特性进行了实验研究。在研究中使用了完全开发的喷嘴。流动结构进行了研究，使用激光多普勒测速仪和壁面压力测量。滞止努塞尔数相关的挡板间距小于一个直径。传统的努塞尔数依赖于Re 1 - 2的冲击射流运输观察。从理论上探讨了实验观察到的努塞尔数和隔板间距之间的幂律关系Nu 0 <$（z d）− 0.288。隔板间隙之间的加速流体的影响以及局部湍流的显著增加导致随着隔板间距的减小而显著增加的局部热传递。在局部传热的内部和外部峰值包围的驻点最小值观察到的挡板间距小于ZD = 0.25。这些主要和次要的最大值的解释加速径向流在出口处的喷射管和观察到的局部最大值的湍流，分别。这些结论是从湍流结构和壁面压力测量的观测结果中得出的。局部努塞尔数的外峰被发现径向向外移动较大的挡板间距和较高的射流雷诺数。
The local heat transfer characteristics of air jet impingement at nozzle-plate spacings of less than one nozzle diameter have been examined experimentally using an infrared thermal imaging technique. Fully-developed nozzles were used in the study. The flow structure was investigated using laser-Doppler velocimetry and wall pressure measurements. The stagnation Nusselt number was correlated for nozzle-plate spacings of less than one diameter. The customary Nusselt number dependence on Re 1 2 for impinging jet transport was observed. A power-law relationship between Nusselt number and nozzle-plate spacing of the form Nu 0∼(z d)− 0.288 observed experimentally is explored from theoretical considerations. The effects of accelerating fluid between the nozzle-plate gap as well as a significant increase in local turbulence leads to substantially increased local heat transfer with decreased nozzle-plate spacing. A stagnation point minimum surrounded by an inner and outer peak in the local heat transfer was observed for nozzle-plate spacings less than z d= 0.25. These primary and secondary maxima are explained by accelerated radial flow at the exit of the jet tube and an observed local maximum in the turbulence, respectively. These conclusions are drawn from observations made relative to the turbulent flow structure and wall pressure measurements. The outer peak in local Nusselt number was found to move radially outward for larger nozzle-plate spacings and higher jet Reynolds numbers.