The critical heat transfer characteristics of an insulated oval duct
The critical heat transfer characteristics of an insulated oval duct
复制标题
DOI：
10.1016/j.enconman.2010.01.019
复制
发表时间：
2010-07
影响因子：
10.4
通讯作者：
King-Leung Wong;W. L. Chen;T. Hsien;H. Chou
中科院分区：
文献类型：
--
作者：
King-Leung Wong;W. L. Chen;T. Hsien;H. Chou
本文采用二维数值分析和一维PWTR模型，结合精确的椭圆形管道表面，对椭圆形管道的临界厚度和中性厚度特性进行了研究。当绝热圆形管道的外半径小于其临界绝热半径时，发生临界传热。传热速率随绝热层厚度的增加而增加，在临界绝热层厚度处达到最大值，然后减小，直至中性厚度点，此时传热速率与非绝热层相同。因此，如果绝缘厚度小于中性绝缘厚度，则任何绝缘努力都是无意义的。这些特性对于小尺寸绝热管道非常重要，特别是在环境空气/气体对流系数低的条件下。研究表明，椭圆形绝热管道的临界现象与圆形绝热管道的临界现象非常相似，只是椭圆轴比越大，其临界厚度和中性厚度越小。
This study is to investigate the characteristics of critical and neutral thicknesses of an insulated oval duct by using two-dimensional numerical analysis and the one-dimensional PWTR model, coupled with accurate oval duct surfaces. Critical heat transfer occurs when the outer radius of an insulated circular duct is less than its critical insulation radius. The heat transfer rate increases with increasing the insulation thickness until the maximum value is reached at the critical insulated thickness, then it decreases until the point of neutral thickness, where the heat transfer rate is the same as that of a non-insulated duct. Thus, any insulation effort is meaningless if the insulation thickness is less than the neutral insulated thickness. These characteristics are very important for small size insulated duct, especially in conditions of low ambient air/gas convective coefficients. It shows in this study that the critical phenomena of an insulated oval duct is very similar to those of an insulated circular duct except it’s critical and neutral thicknesses are smaller for larger oval axes ratio.