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Systematic Research on Free Convection Heat Transfer in a Stably Stratified

稳定分层中自由对流换热的系统研究

基本信息

批准号：
16560179
负责人：
HIMENO Nobuhiro
金额：
$ 2.37万
依托单位：
Shinshu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16560179/
关键词：
Double Diffusion Free Convection Heat Transfer Stably Stratified Fluid Systematic Research Coaxial Cylinder Rectangular Cell

项目摘要

The following three issues have been investigated to conduct a systematic research on free convection heat transfer in a stably stratified fluid.1. Effects of the inner cylinder diameter on free convection heat transfer between coaxial cylindersThe stratified layer was formed using a sucrose aqueous solution, and was heated from the outer cylinder (70mm I.D.) at constant heat flux and cooled from the inner cylinder (15mm, 30mm or 50.8mm O.D.) at constant temperature. As a result, it is found that the early stage heat transfer is affected by the size of the inner cylinder, and the convection heat transfer shows similar characteristics of that between vertical plates, when the inner cylinder diameter becomes large. On the other hand, when the inner cylinder diameter being small, the average heat transfer coefficient approaches the steady state value with time but never exceeds it.2. Effects of a distance between heat transfer plates on free convection heat transfer between vertical platesThe stratified layer was formed using a sucrose aqueous solution, and was heated from one side wall at constant heat flux and cooled from the other side wall at constant temperature. The experiments were conducted for the distance between the heat transfer plates l=10mm, 40mm and 60mm, and the results were compared with those for l=20mm which are reported by the authors. As a result, it has been found that the average heat transfer coefficient becomes great, when the cellular layer thickness equals to the distance between the heat transfer plates.3. Numerical analysis on free convection heat transfer in a rectangular cellNumerical analysis has been performed on free convection heat transfer in a rectangular cell for wide rages of aspect ration 0.1-20 and Ra number 10^3-10^7, and correlation equations for the heat transfer coefficient have been developed to construct a theoretical model for analyzing the heat transfer in a stably stratified fluid.

为了对稳定分层流体中的自由对流换热进行系统研究，主要从以下三个问题出发： 1．内筒直径对同轴筒之间自由对流换热的影响使用蔗糖水溶液形成分层层，并从外筒（70mm I.D.）以恒定热通量加热，并从内筒（15mm、30mm或50.8mm O.D.）恒温冷却。结果发现，早期传热受内筒尺寸的影响，当内筒直径变大时，对流换热表现出与垂直板间的对流换热相似的特性。另一方面，当内筒直径较小时，平均传热系数随时间接近稳态值，但从未超过稳态值。2．传热板间距对垂直板间自由对流换热的影响采用蔗糖水溶液形成分层层，从一侧壁以恒定热通量加热，从另一侧壁以恒定温度冷却。对传热板间距l=10mm、40mm、60mm进行了实验，并将结果与作者报道的l=20mm时的结果进行了比较。结果发现，当多孔层厚度等于传热板之间的距离时，平均传热系数变大。 3．矩形单元内自由对流换热的数值分析对长径比为0.1-20、Ra数为10^3-10^7的矩形单元内的自由对流换热进行了数值分析，建立了传热系数的相关方程，建立了稳定分层流体传热分析的理论模型。