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

基本信息

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

项目摘要

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.

为了提高喷气机撞击冷却装置的性能，研究了大规模纵向涡旋和自激发振荡的有效性。注意以下三项。（1）喷嘴的几何配置，（2）自激振荡的频率和（3）涡流结构的模式。还研究了喷气机的相互作用，以及与传热系数和流速曲线相关的测量技术的发展。 LDV和PIV系统分别用于测量局部速度波动和横截面矢量分布。使用热色液液晶片测量传热目标壁的温度，其颜色图像是用CCD摄像头拍摄的。应用神经网络方法将颜色图像转换为壁温度分布。如果距离倾斜排入主要流动，则一对大规模的反旋转涡旋在用激光板照明的横截面中清楚地看到，该激光板在相似的边界条件下进行了数值预测。传统垂直撞击射流与当前的倾斜射流之间的比较揭示了倾斜射流对垂直射流的优越性。在自激发振荡射流的情况下，在相对较小的撞击距离条件下，停滞区域中的努塞尔数分布的模式发生了巨大变化。仅需要少量变化喷气喷嘴的几何尺度才能产生可听到的振荡，而没有任何额外的能量。因此，发现激发振荡对射流撞击传热具有很大影响。与振荡影响最大的情况相对应，基于振荡频率的曲线数量约为0.3。