Control of Natural Convection by Local Cooling or Heating with a Row of Heat Pipes

通过一排热管进行局部冷却或加热来控制自然对流

• 批准号: 05650199
• 负责人: MASUOKA Takashi
• 金额: $ 1.41万
• 依托单位: Kyushu Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05650199/
• 关键词: Natural Convection; Boundary Layr; Control of Convection; Thermal Screen; Heat Pipe

This study is concerned with a method for controlling natural convection by utilizing a thermal screen consisting of a row of heat pipes with very high effective thermal conductivity. Experimental and analytical studies have been made on the effects of the heat extraction or heat release through the thermal screen on the developments of the natural convecion boundary layr along a vertical heating wall and of the buoyant plume above a line heat source.First, the thermal screen is placed in parallel with a vertical heating wall in an air environment. The experimental temperature distributions obtained by the visual observations using a thermal video system and thermocouples show that the thermal boundary layr becomes thinner than that of the system without screen when the temperature of the screen is closer to the ambient temperature. On the other hand, in the case that the temperature of the screen is close to that of the vertical wall, the thickness of thermal boundary layr increases. … More Therefore, heat transfer from the vertical wall is enhanced as the screen temperature decreases to the environment temperature and reduced as it increase to the wall temperature. The experiments also show that the closer location of the screen to the vertical heating wall is effective for the control of the natural convection heat transfer. Two dimensional-numerical calculation has been made to clarify the mechanism of controlling theconvective pattern and it is found that the thermal screen can change the buoyancy force by affecting the temperatures of in-flowing and out-flowing fluids.Secondly, experiments have been carried out for the buoyant plume arising from a line heat source. The thermal screen is located above the heat source to control the development of the plume. Visual observaions of the plume using a Mach-Zehnder interferometer and the experimental temperature distributions show the expansion or contraction of the plume at the location of the screen. The thermal screen with a small permeability can change the characteristics of the buoyant plume and the effect of the heat extraction or the heat release is marked, although the effect of the screen is reduced with the increase in permeability. Also, the experimental results show that the thermal screen can suppress or promote an oscillation of the plume by changing its temperature level. It is confirmed by the numerical study that the heat transfer rate depends on the permeability of the screen and the heat extraction or heat release can modify the buoyancy force because the screen introduce a strong uniformity in the temperature distributions.Then, it is concluded that the thermal sscreen can control the characteristics of both natural convection along the vertical wall and buoyant plume, depending on the location, permeability and the temperature level of the screen. Less

本文研究了一种利用由一排具有很高有效导热系数的热管组成的热屏来控制自然对流的方法。本文通过实验和分析研究了热屏取热或放热对沿着垂直加热壁面自然对流边界层发展和线热源上方浮力羽流发展的影响。利用热摄像系统和热电偶对热边界层温度分布进行了直观观测，结果表明，当屏幕温度接近环境温度时，热边界层比无屏幕系统的热边界层薄。另一方面，在屏壁温度接近垂直壁温度的情况下，热边界层厚度增加。 ...更多信息 因此，从垂直壁的热传递随着屏幕温度降低到环境温度而增强，并且随着屏幕温度升高到壁温而减少。实验还表明，屏壁位置越靠近垂直加热壁面，对控制自然对流换热效果越好。通过二维数值计算，阐明了热屏控制对流场的机理，发现热屏可以通过影响流入和流出流体的温度来改变浮力。其次，对线热源产生的浮力羽流进行了实验研究。热屏位于热源上方，以控制羽流的发展。利用马赫-曾德尔干涉仪对羽流进行了目视观测，并通过实验测量了羽流的温度分布，结果表明羽流在屏面处有膨胀或收缩的现象。渗透率小的热屏可以改变浮力羽流的特性，热提取或热释放效果显著，但随着渗透率的增加，热屏的效果减弱。实验结果还表明，热屏可以通过改变羽流的温度水平来抑制或促进羽流的振荡。数值研究表明，热屏的渗透性决定了热屏的传热速率，热屏的取热或放热可以改变热屏的浮力，热屏可以控制竖直壁面沿着自然对流和浮力羽流的特性，这取决于热屏的位置。渗透率和屏幕的温度水平。少

项目成果

Takashi, MASUOKA: "Effect of Thermal Screen on Bouyant Plume above Line Heat Source" Proc.of the 31th Japan National Heat Transfer Symposium. (1995)

Takashi, MASUOKA：“热屏对线热源上方浮力羽流的影响”第 31 届日本全国传热研讨会论文集。

増岡 隆士: "熱スクリーンによる自然対流の制御" 第31回日本伝熱シンポジウム講演論文集. 1. 331-333 (1994)

Takashi Masuoka：“使用热屏控制自然对流”第 31 届日本传热研讨会论文集 1. 331-333 (1994)。

増岡 隆士: "熱スクリーンによる自然対流境界層制御" 第31回日本伝熱シンポジウム講演論文集. (1994)

Takashi Masuoka：“使用热屏的自然对流边界层控制”第 31 届日本传热研讨会论文集（1994 年）。

増岡 隆士: "線熱源上の対流プルームに及ぼす熱スクリーンの影響" 第32回日本伝熱シンポジウム講演論文集. (1995)

Takashi Masuoka：“热屏对线性热源上方对流羽流的影响”第 32 届日本传热研讨会论文集（1995 年）。

Takashi, MASUOKA: "Control of Natural Convection by Local Cooling or Heating Through a Thermal Screen" Proc.of the 32th Japan National Heat Transfer Symposium. No.1. 331-333 (1994)

Takashi, MASUOKA：“通过热屏局部冷却或加热控制自然对流”第 32 届日本全国传热研讨会论文集。