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首页> 外文期刊>International Journal of Heat and Mass Transfer >The effect of jet location and duty cycle on the fluid mechanics of an unconfined free jet and its heat transfer on an impinging plate
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The effect of jet location and duty cycle on the fluid mechanics of an unconfined free jet and its heat transfer on an impinging plate

机译：射流位置和占空比对无限制自由射流的流体力学及其在撞击板上的传热的影响

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摘要

Unsteady heat transfer caused by an unconfined impinging air jet is experimentally studied. Four test cases are considered, two pulse frequencies and two duty cycles. The outcome of this experimental study is compared to that of steady jet impinging heat transfer relations and data. Characterization of the pulsed air jet is conducted using a hot wire anemometer at twelve discrete locations for each pulse case considered. The local instantaneous velocities collected were then used to calculate time averaged mean velocity, and turbulent intensity. A power spectral distribution was produced for each of the jet flows to acquire insight toward the most effective jet flow characteristics for heat removal on an impingement surface. An infrared (IR) camera was used to determine a full field instantaneous heat transfer coefficient for each of the pulse cases and a nozzle to plate setback distances. All data was collected over a Reynolds number range of 866 and 3776. The jet characterization suggested that a setback distance of three hydraulic diameters (as opposed to one-half or six) produces the most effective power spectral density given a pulse frequency of 5 Hz and a duty cycle of 50%. The infrared camera data collected argues against the conclusions drawn from the hot wire data suggesting that the most effective setback distance is six hydraulic diameters and with a frequency of 10 Hz and a duty cycle of 50%. All data provides similar evidence that the duty cycle over a pulse period has a larger impact on the heat transfer of an impinging air jet than that of pulse frequency.
机译：实验研究了由无限制的撞击空气射流引起的不稳定的传热。考虑了四个测试用例，两个脉冲频率和两个占空比。将该实验研究的结果与稳定射流撞击传热关系和数据进行了比较。对于每个所考虑的脉冲情况，使用热线风速计在十二个离散位置进行脉冲空气喷射的表征。然后使用收集的局部瞬时速度来计算时间平均平均速度和湍流强度。为每个射流产生了功率谱分布，以了解最有效的射流特性以消除撞击表面上的热量。红外（IR）摄像机用于确定每个脉冲情况的全场瞬时传热系数以及喷嘴到板的缩进距离。所有数据都是在866和3776的雷诺数范围内收集的。喷射特性表明，在5 Hz的脉冲频率下，三个液压直径的缩进距离（而不是一半或六个）产生了最有效的功率谱密度。占空比为50％。收集的红外热像仪数据与从热线数据得出的结论相矛盾，该结论表明最有效的后退距离是六个液压直径，频率为10 Hz，占空比为50％。所有数据都提供了类似的证据，即脉冲周期内的占空比对撞击空气射流的传热影响比脉冲频率的影响大。

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  • 作者

    W.R. Marcum; S.R. Cadell; C. Ward;

  • 作者单位

    Oregon State University, Department of Nuclear Engineering and Radiation Health Physics, 116 Radiation Center, Oregon State University, Comallis, OR 97330, United States;

    Oregon State University, Department of Nuclear Engineering and Radiation Health Physics, 116 Radiation Center, Oregon State University, Comallis, OR 97330, United States;

    Oregon State University, Department of Mechanical, Industrial, and Manufacturing Engineering, 204 Rogers Hall, Oregon State University, Corvallis, OR 97331, United States;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Air jet; Impingement; Pulse; Duty cycle;

    机译：喷气撞击脉冲;占空比;

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