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Dynamic Solidification of Binary Aqueous Solution

二元水溶液的动态固化

基本信息

批准号：
14550174
负责人：
KIMURA Shigeo
金额：
$ 2.56万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550174/
关键词：
Phase Change Solidification Natural Convection Convection Heat transfer Mushy Layer Double Diffusion Numerical Analysis Porous Medium 連成熱伝達対流熱伝達レイリー数ヌッセルト数

项目摘要

In this study solidification process of binary aqueous solution is investigated. Main goal of the present work is to develop a one-dimensional approximate model to predict the time-dependent behavior of the solid layer growth and decay. Since the solid layer formed in the aqueous solution becomes mushy (a porous layer), we first study the solidification in the water-saturated porous medium. Particularly the solid layer response when the cooling temperature varies with time is our major interest. One-dimensional model is developed in order to predict the temporal solid layer thickness. Experiments using a cubic container filled with water-saturated glass beads are carried out for testing the validity of the proposed one-dimensional model. Two-dimensional numerical analysis is also performed for the same purpose. It is found that the proposed one-dimensional model accurately predicts the both experimental and numerical results. Next we extend our one-dimensional model to solidification o … More f binary aqueous solution. Assuming the constant solid fraction in the mushy layer and the specified heat flux at the solid-fluid interface, which is effectively simulating the convective heat flux at the interface, the time-dependent heat conduction equation in the solid layer (mushy layer) and the thermal energy balance at the interface are combined to yield the transcendental equation for the unknown thickness of the mushy layer. Experiments are also carried out using the cubic container filled with aqueous sodium nitrate. Two different thermal boundary conditions are employed ; one is cooled from above, and the other is cooled from below. The former is characterized by the presence of vigorous convection in the liquid region, while the latter is dominated by diffusion. The solid-layer thickness and the solid fraction in the mush predicted by one-dimensional model again agree well with the experimental results, for the both thermal boundary conditions. It is found that the solid fraction in the mush formed by cooling from above has greater values than those by cooling from below. This is due to the different concentration of the interstitial solution in the mush. Since the mass diffusion is very small relative to thermal diffusion, the concentration in the interstice tends to accumulate when the system is cooled from below. We also investigate mixed convection heat transfer from a vertical cooled or heated cylinder. This has an important application for evaluating heat transfer rate of geothermal heat exchangers. Less

本文研究了二元水溶液的凝固过程。本工作的主要目标是建立一个一维的近似模型来预测固体层的生长和衰减的时间依赖行为。由于在水溶液中形成的固体层变成糊状（多孔层），我们首先研究了水饱和多孔介质中的固化。特别是当冷却温度随时间变化时的固体层响应是我们的主要兴趣。为了预测固体层厚度，建立了一维模型。利用装满水饱和玻璃珠的立方体容器进行实验，以检验所提出的一维模型的有效性。二维数值分析也是出于同样的目的。结果发现，所提出的一维模型准确预测的实验和数值结果。接下来，我们扩展我们的一维模型凝固 ...更多信息 f二元水溶液。假设糊状层中的固含率为常数，固液界面处的热流密度为一定值，有效地模拟了界面处的对流热流密度，将固体层（糊状层）中的时变热传导方程和界面处的热能平衡结合起来，得到糊状层厚度未知的超越方程。实验也是用装有硝酸钠水溶液的立方体容器进行的。采用了两种不同的热边界条件;一种是从上面冷却，另一种是从下面冷却。前者的特点是在液体区域中存在强烈的对流，而后者是由扩散为主。在两种热边界条件下，一维模型预测的固相层厚度和固相率与实验结果吻合较好。结果表明，从上方冷却形成的糊状物中的固体分数比从下方冷却形成的糊状物中的固体分数大。这是由于糊状物中间隙溶液的浓度不同。由于质量扩散相对于热扩散非常小，当系统从下面冷却时，在蒸发器中的浓度倾向于积累。我们也研究了垂直冷却或加热圆柱的混合对流换热。这对评价地热换热器的传热率具有重要的应用价值。少