An Experimental Study on New Technology of Dynamic Cooling with Jet Impingement

射流冲击动态冷却新技术的实验研究

• 批准号: 10450086
• 负责人: SUZUKI Kenjiro
• 金额: $ 8.51万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10450086/
• 关键词: Jet Impingement; Crossflow; Heat Transfer Control; Heat Transfer Measurement; Velocity Measurement

Effectiveness of large-scale longitudinal vortices and self-excited oscillation generated by a jet on impingement heat transfer were investigated in order to improve the performance of jet impingement cooling devices. Attention was paid to the following three items; (1) geometrical configurations of jet nozzle, (2) frequencies of the self-excited oscillation, and (3) patterns of vortical structures. The interaction of jets were also investigated together with the development of measuring techniques related to the heat transfer coefficients and flow velocity profiles. LDV and PIV systems were used to measure local velocity fluctuations and cross-sectional velocity vector distributions, respectively. The temperatures of the heat transfer target wall were measured using thermochromic liquid crystal sheets, the color images of which were taken with a CCD camera. Neural network method was applied to transform the color images into the wall temperature distributions. In the case of the jet obliquely discharged into a main flow, a pair of large-scale counter-rotating vortices was clearly visualized in the cross-section illuminated by a laser sheet, which was numerically predicted under similar boundary conditions. Comparison between the conventional vertical impinging jet and the present oblique jet reveals the superiority of the oblique jet to the vertical one. In the case of the self-excited oscillation jet, the patterns of Nusselt number distributions in the stagnation region drastically change under the conditions of relatively small impingement distance. Only small change of the geometric scales of the jet nozzle was required to generate the audible oscillation without any extra energy to the jet. Thus, the excited oscillation was found to have a great influence on the jet impingement heat transfer. Corresponding to the cases most influenced by the oscillation, Strouhal number based on the oscillation frequency was around 0.3.

为了提高射流冲击冷却装置的性能，研究了射流产生的大尺度纵向涡和自激振荡对冲击传热的影响。会议注意了下列三个项目：(1)喷嘴的几何构型；(2)自激振荡的频率；(3)涡旋结构的模式。射流的相互作用也进行了研究，并发展了与传热系数和流速剖面相关的测量技术。LDV和PIV系统分别用于测量局部速度波动和横截面速度矢量分布。利用热致变色液晶片测量了传热靶壁的温度，并利用CCD相机拍摄了传热靶壁的彩色图像。采用神经网络方法将彩色图像转化为壁面温度分布。在射流斜向进入主流的情况下，在激光照射的截面上可以清晰地看到一对大尺度的反向旋转涡，并在类似的边界条件下进行了数值预测。通过对传统垂直冲击射流与斜向射流的比较，揭示了斜向射流相对于垂直冲击射流的优越性。对于自激振荡射流，在较小的撞击距离条件下，滞止区努塞尔数分布模式发生了剧烈变化。只需要喷嘴几何尺度的微小变化就能产生可听振荡，而不需要给射流带来额外的能量。由此可见，激发态振荡对射流冲击换热有很大的影响。与受振荡影响最大的情况相对应，基于振荡频率的Strouhal数在0.3左右。

项目成果

Cvetinovic,D.B., 他3名: "Visualization on Flow Structures of a Self-sustained Oscillating Jet and its Enhanced Region of Impingement Heat Transfer"Proc. 9th Int'l Symp. On Flow Visualization. (in printing). (2000)

Cvetinovic，D.B. 和其他 3 人：“自持振荡射流的流动结构及其增强的冲击传热区域”Proc. 9th Intl Symp（关于流动可视化）。

Nakabe,K., 他5名: "Vortical Structures of a Jet Vertically or Obliquely Discharged into a Crossflow"Proc. 8th Int'l Symp. On Transport Phenomena and Dynamics of Rotating Machinery. (in printing). (2000)

Nakabe, K. 和其他 5 人：“垂直或倾斜喷射成横流的涡流结构”Proc. 8th Intl Symp. On Transport Phenomena and Dynamics of Rotating Machinery (2000)。

E.Fornalik 他4名: "Visualization of Heat Transfer Enhancement Regions Modified by the Interaction of Inclined Impinging Jets into Crossflow"Machine Visions & Graphics. Vol.18,No,4. 597-610 (1999)

E. Fornalik 和其他 4 人：“通过倾斜冲击射流与横流的相互作用修改的传热增强区域的可视化”，机器视觉与图形，第 18 卷，第 597-610 期（1999 年）。

E.Fornalik 他4名: "Interactions of Longitudinal Vortices Generated by Twin Inclined Jets and Enhancement Regions of Impingement Heat Transfer"Proc. 3^<rd> Turbulence, Heat and Mass Transfer. (in printing). (2000)

E. Fornalik 和其他 4 人：“双倾斜射流产生的纵向涡流与冲击传热增强区域的相互作用”Proc. 3^<rd> 湍流、传热和传质（印刷中）。

Nakabe,K., 他3名: "Experimental Study of Heat Transfer Characteristics of an Impinging Jet with Acoustically Self-Excited Oscillation"Proc. 2nd Int'l Symp. On Adv. Energy Conversion System. 88-89 (1998)

Nakabe，K. 和其他 3 人：“声学自激振荡冲击射流的传热特性的实验研究”Proc. 2nd Intl Symp。