权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Turbulent thermal mixing of hot and cold flows and flow structure in mixing T-junction

冷热流湍流热混合及混合T型接头的流动结构

基本信息

批准号：
14350106
负责人：
HIROTA Masafumi
金额：
$ 6.21万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14350106/
关键词：
Mixing T-junction Turbulent thermal mixing Dynamic PIV LIF Thermal striping 合流配管乱流混合乱流熱拡散 PIV

项目摘要

A piping system in a nuclear power plant has many T-junctions, in which hot and cold fluids meet with various velocity ratios and are mixed together. It is now pointed out that spatial and temporal temperature fluctuations due to the mixing of hot and cold water induce high-cycle thermal fatigue of the piping structure around a T-junction. This phenomenon is called thermal striping and is a serious problem for the safety design of nuclear power plants. Although several researches have been conducted on this issue from a viewpoint of thermo-fluids engineering, detailed unsteady flow structure and mixing characteristics around the T-junction are not well understood yet. In particular, detailed data on the counter-type mixing flow are quite scarce in comparison with the cross-type mixing flow. In view of the above situation, we investigated experimentally the unsteady flow and thermal mixing characteristics in a counter-type T-junction. The T-junction in the piping system was modeled by a … More mixing tee with square cross sections, in which the mixing channel was connected with the main and counter channels at right angles and the flow in the main channel collided head-on with that in the counter channel. Reynolds number of the main-channel flow was fixed at 3500, and the velocity ratio of the counter-channel flow to main one was changed from 1.0 to 5.0. For a better understanding of the unsteady flow characteristics, we used PIV with the combination of a high-speed camera and a continuous wavelength YVO_4 laser, which enabled us to measure the velocity distribution with a time resolution of 1 kHz. The temperature measurement was replaced by the concentration measurement based on the heat and mass transfer analogy. PLIF was used for the concentration measurement, in which Rhodamine 6G was dissolved in the main channel flow as a fluorescence tracer.It was found that the flow in the mixing channel had a complex three-dimensional and unsteady structure accompanied by the flow separation, reattachment, and longitudinal vortices. The concentration (temperature) distribution was closely related to those flow characteristics. To identify the coherent flow structures, the proper orthogonal decomposition (POD) analysis was applied to the fluctuating velocity field in the mixing channel. The unsteady vortex motion along the shear layer and the wobbling motion of the interface between the main-channel and counter-channel flows could be extracted, both of which produced high concentration fluctuation and could play an important role in the thermal striping process. Less

核电站的管道系统有许多t形接头，冷热流体在其中以不同的速度比相遇并混合在一起。现在指出，由于冷热水混合引起的时空温度波动会引起t型接头周围管道结构的高周热疲劳。这种现象被称为热条纹，是核电站安全设计的一个严重问题。虽然从热流体工程的角度对这一问题进行了一些研究，但对t型结周围的非定常流动结构和混合特性还没有很好的了解。特别是，与交叉型混合流相比，反向型混合流的详细数据相当缺乏。针对上述情况，本文对反型t型结的非定常流动和热混合特性进行了实验研究。管道系统中的t型接头采用方形截面的混合三通来模拟，其中混合通道与主通道和反通道成直角连接，主通道内的气流与反通道内的气流正面碰撞。将主流道的雷诺数固定为3500，将反流道与主流道的流速比由1.0改为5.0。为了更好地了解非定常流动特性，我们将PIV与高速摄像机和连续波长YVO_4激光器相结合，使我们能够以1 kHz的时间分辨率测量速度分布。基于传热传质类比的浓度测量取代了温度测量。使用PLIF进行浓度测量，其中罗丹明6G作为荧光示踪剂溶解在主通道流中。研究发现，混合通道内的流动具有复杂的三维非定常结构，并伴有流动分离、再附着和纵向涡旋。浓度（温度）分布与这些流动特性密切相关。为了识别混合通道内的相干流动结构，对混合通道内的波动速度场进行了适当的正交分解分析。可以提取出沿切变层的非定常涡旋运动和主流道与反流道交界面的摆动运动，这两种运动都会产生高浓度波动，在热条形过程中发挥重要作用。少