电子设备封闭腔内自然对流冷却效果数值分析

Numerical analysis of natural convection cooling effect in closed cavity of electronic equipment

为了研究安装于封闭空间内的电子设备散热元件属性及空间位置对腔内自然对流传热特性的影响,该文采用FLUENT14.5软件中的RNGk-ε湍流模型对流体为空气、高宽比为1的封闭腔内温度场、流场、壁面传热能力进行了数值分析。结果表明:在热壁面1/3高度处布置1个导热翅片时热壁面的平均Nu数比相同位置布置绝热翅片时提高了9.67%;在热壁面1/3高度处、冷壁面2/3高度处同时各布置1个导热翅片时热壁面平均Nu数可取得双翅片工况的最大值39.94,比单翅片的最优工况平均Nu数提高了14.34%。本文研究结果对于改善工农业工程中电子元器件的自然对流冷却效果、优化散热元器件的空间布置具有一定的理论指导意义。

Natural convection in closed cavity has been received considerable attention due to its widely applications in industry,such as in solar energy collectors design,cooling of electronic instruments,energy saving of building and nuclear reactor design,the study of natural convection mechanism in enclosed cavity is of great practical significance for improving the comprehensive performance of these systems.With the rapid development of science and technology,more and more heat sources and components are located in the same enclosed cavity,which will lead to large number of heat generation.How to arrange the heat source elements is very important to the cooling and reliability of the system by the natural convection heat transfer.Lots of studies have shown that the fins attached to the vertical walls inside the cavity can enhance the heat transfer rate in the cavity.In order to study the effect of the material and space position of heat radiation in enclosed space on the heat transfer characteristics of natural convection,the RNG k-εmodel of FLUENT14.5 was adopted to analyze the temperature field,flow field,local Nusselt numbers and the average Nusselt numbers of the vertical wall of the air-filled cavity(left side was hot wall,right side was cold wall and the top side was the heat source)with aspect ratio of 1.The results showed that the heat transfer enhancement of the cavity was strongly dependent on the position and material of the fins attached to the vertical walls.The influence of single fin and double fin on the horizontal velocity near the top of the cavity was weak,and the disturbance to the horizontal velocity field near the bottom of the cavity was intense,and the influence trend was very close.This phenomenon was not consistent with that of without heat source.The effect of fins on the horizontal velocity in the core region of the cavity was quite different:the disturbance of single fin on the lower position of the core region of the cavity was more obvious,while the disturbance of double fins on the upper region was more intense.Different number of fins lead to different distribution characteristics of temperature field in the enclosed cavity by changing the flow field structure.When the adiabatic fin was located at 1/6 height above the bottom of the hot wall,the average heat transfer capacity of the hot wall was the strongest.When the heat conducting fin was located at 1/3 height above the bottom of the hot wall,the average heat transfer capacity of the hot wall was the strongest.The combination of 1/3 height above the bottom of the hot wall and 2/3 height above the bottom of the cold wall made the average heat transfer capacity of the hot wall the strongest.The average Nu number of thermal conductive fins arranged at 1/3 height above the bottom of the hot wall was maximum,which was 34.93 and 9.67%higher than that of adiabatic fin arranged at the same location.The average Nu number of thermal conductive fins arranged at 1/3 height above the bottom of the hot wall and 2/3 above the bottom of the cold wall was maximum,which was 14.3%and higher than that of thermal conductive fins arranged only at 1/3 above the bottom of the hot wall.The study has a certain theoretical significance for improving the natural convection cooling effect of electronic components in industrial and agricultural engineering and optimizing the spatial location of heat dissipation components.