Study On Natural Convection Heat Transfer Characteristics Of Turbulent Flow In Enclosure With Built-in Fins

The natural convection heat transfer process is widely applied in various industrial production and process treatment.The research on the natural convection heat transfer characteristics in enclosure with heated sidewalls is in great demand and the related research has become a hot topic in the fields of flow and heat transfer.It has important research value in optimizing industrial design and prolonging the service life of electronic components by arranging fins on the inner wall of the enclosed cavity and simulating the cooling of electronic components in the enclosed cavity by influencing the structure and development of boundary layer.The integrated effects on the natural convection and radiation coupling heat transfer in the cavity of the internal heat source and the number,position,material of rectangular fins arranged on the inner wall of the enclosure were studied based on this engineering application background in this article(R?=1.58×10~9).The main work of this paper is as follows:(1)The IFA300 hot wire anemometer and thermocouple was used to test the average velocity and average temperature of the measuring points at the same time,the velocity from the wall facing to the cavity core area and the temperature distribution changes with height are obtained.The results show that the average temperature gradually increases with the increasing height and the thickness of velocity boundary layer and the temperature boundary layer gradually increases along the wall surface.(2)The effect of convection and heat transfer inside the cavity when the individual heat-conducting fins and the heat-insulating fins located at different positions on the hot wall surface was numerical analysis.The results show that in the conditions of no heat source and built-in heat source in the enclosure,the average Nu number of the hot wall surface is the maximum,the heat transfer efficiency between the wall surface and the interior of the cavity is the highest and the convection heat exchange ability of the fluid inside the cavity is the strongest when the heat conducting fins are located at the upper 1/3 height from the bottom surface along the hot wall.While the average Nu number of the hot wall surface is maximum,the heat transfer efficiency between the wall surface and the interior of the cavity is the highest and the convection heat exchange ability of the fluid inside the cavity is the strongest when the heat insulating fins are located at the upper 1/6 height from the bottom surface along the hot wall.(3)One fin was arranged on the hot wall surface and the cold wall surface respectively.The influence of fin position and fin material on convection and heat transfer inside the cavity was numerically analyzed.The results show that,in both cases with no heat source and built-in heat source in the enclosure,regardless of the heat-conducting fins or the heat-insulating fins,the average Nu number is maximum,the heat transfer efficiency between the wall and the interior of the cavity is the highest and the convection heat exchange ability of the fluid inside the cavity is the strongest when the fins are located at 1/3 height of the hot wall surface and 2/3 height of the cold wall surface.(4)When the heat-conducting fin is located at the 1/3 height of the hot wall surface,the change rate of vertical velocity along the height direction at the half-width of the cavity increases while the horizontal velocity near the cold wall surface at the half height of the cavity does not change much with the increasing wall surface emissivity.The horizontal velocity near the hot wall surface gradually increases with the increasing wall surface emissivity.The influence of radiation on the distribution of the horizontal speed and the average temperature along the height direction at the half width of the cavity is very weak.However,compared with the case without considering the radiation,the horizontal wave velocity and peak velocity near the top surface and the bottom surface are relatively large and the average temperature is significantly increased near the bottom surface.When considering radiation,the local shear stress in the lower region of the hot wall surface is smaller than that in no considering radiation condition.As the emissivity of the wall surface increases,the local shear stress in the upper region of the hot wall gradually increases and the increasing amplitude gradually decreases.When the wall surface emissivity are 0,0.3,0.6 and 0.9,the average Nu number of the hot wall surface are 84.14,117.75,158.65 and 206.12,respectively.(5)When the thermal fin was arranged at the 1/3 height of the hot wall surface and 2/3height of the cold wall surface,the positive vertical velocity at the half width of the cavity is significantly higher than that in no considering radiation condition when the emissivity of the wall surface is 0.6.While the negative vertical velocity at the half-width of the cavity is significantly improved than that in no considering radiation condition when the wall surface emissivity is 0.9.The changing trend of the horizontal velocity and average temperature along the height direction at the half-width of the cavity are basically the same when considering radiation.However,compared with the case without considering radiation,the trough value and peak value of the horizontal velocity near the top surface and the bottom surface are relatively large and the average temperature near the bottom surface has a obvious increase.While the changes trend of the vertical velocity and horizontal velocity along the horizontal direction at the half height of the cavity are basically the same at different wall surface emissivities.When considering radiation,the local shear stress in the lower region of the hot wall surface is smaller than that in no considering radiation condition and the local shear stress in the upper region is relatively large.When the wall surface emissivity are 0,0.3,0.6and 0.9,the average Nu number of the hot wall surface are 88.17,124.40,165.16 and 212.69,respectively.The effect of natural convection heat transfer on the turbulent air in an enclosure by location and number of rectangular fin,internal heat source,fin material and wall emissivity was initially studied in this article.However,further experimental research is needed to obtain accurate and practical research results.