水平同心圆柱环内自然对流换热研究  

Natural convection heat transfer in horizontal concentric cylindrical annuli

作　　者：杨万鑫 邹声华[1] 李文菁[3] 胡琦 YANG Wanxin;ZOU Shenghua;LI Wenjing;HU Qi(School of Civil Engineering,Hunan University of Science and Technology,411201 Xiangtan,China;Hunan Architectural Design Institute Group Co.,LTD.,410000 Changsha,China;School of Architectural Engineering,Hunan Institute of Engineering,411104 Xiangtan,China)

机构地区：[1]湖南科技大学土木工程学院,湘潭411201 [2]湖南省建筑设计院集团股份有限公司,长沙410000 [3]湖南工程学院建筑工程学院,湘潭411104

出　　处：《应用力学学报》2024年第1期206-215,共10页Chinese Journal of Applied Mechanics

基　　金：国家自然科学基金资助项目(No.51274098,51134005)。

摘　　要：外壁温度高于内壁温度的水平同心圆柱环形结构因具有良好的隔热效果,在工程上得到了广泛的应用,而水平同心圆柱环形结构的隔热降温效果受环内流体流动换热影响大,且目前缺乏外壁温度高于内壁温度的水平同心圆柱环内自然对流换热特性研究,因此针对外壁温度高于内壁温度的水平同心圆柱环形结构,数值模拟研究了普朗特数为0.7情况下间隙比(内圆直径与环间距之比,即δ)在0.1~14以及瑞利数在103~107时环内自然对流流动模式与传热。使用流线和等温线分别表示出计算的流动模式和温度场,并研究了间隙比和瑞利数对圆柱环内壁面的平均努谢尔特数的影响。研究发现:在低瑞利数时整个间隙比范围内都存在稳定的月牙形流型,此外还观察到4种不同的流动模式,即二维漏斗振荡流、三维螺旋流、二维多涡流、二维多涡振荡流。这4种流动模式在较高的瑞利数时出现,具体取决于间隙比。根据流动模式的分布特征,整个间隙比可分为3部分,即宽间隙(δ=0.1~2)、中等间隙(δ=2~8)和窄间隙(δ=8~14),给出了不同间隙比范围内环内壁面平均努谢尔特数与间隙比和瑞利数的相关方程,其相关系数(R^(2))大于0.990 2。Natural convection in a horizontal concentric cylindrical annulus with the outer wall temperature higher than the inner wall temperature has received wide engineering applications due to its good thermal insulation effect.The thermal insulation and cooling effect of the horizontal concentric cylindrical annuli is greatly affected by the fluid flow and heat transfer in the annuli,and there is currently a lack of research on the natural convection heat transfer characteristics in the horizontal concentric cylindrical annuli with the outer wall temperature higher than the inner wall temperature.A numerical study of natural convection and heat transfer in horizontal concentric cylindrical annuli with the outer wall temperature higher than the inner wall temperature is performed to investigate the gap ratio and Rayleigh number effect on flow and heat transfer characteristics of air(Pr=0.7).The gap ratio(a ratio of the inner diameter to the gap width of the annulus,namelyδ)in the range of 0.1 to 14 and the Rayleigh number over several orders of magnitude(103≤Ra≤107)are considered.The computed flow patterns and temperature fields are shown by means of streamlines and isotherms,respectively,and the effect of gap ratio and Rayleigh number on the average Nusselt number of the inner wall of a cylindrical annulus is also presented.The results show that a two-dimensional stable unicellular flow pattern occurs at low Rayleigh numbers throughout the whole range of gap ratios,and four different flow patterns are also observed,which are a two-dimensional funnel oscillatory flow,a three-dimensional spiral flow,a two-dimensional multicellular flow and a two-dimensional multicellular oscillatory flow.These four flow patterns appear at relatively high Rayleigh numbers depending on the gap ratio.According to the distribution characteristics of flow patterns,the gap ratio can be divided into three parts,namely,wide gap(δ=0.1-2),moderate gap(δ=2-8)and narrow gap(δ=8-14).In each part,correlating equations of the average Nusselt n

关 键 词：水平同心圆柱环 数值模拟 自然对流 流动模式 传热 

分 类 号：O351[理学—流体力学]