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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/2288

    Title: 輻射傳遞對磁流體自然對流影響之研究;Effects of radiative transfer on hydromagnetic natural convection
    Authors: 蔡祥霖;Shiang-Lin Tsai
    Contributors: 機械工程研究所
    Keywords: 自然對流;磁流體;熱輻射;natural convection;radiation;Magnetodrodynamics
    Date: 2004-06-28
    Issue Date: 2009-09-21 11:42:53 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 現有磁流體熱輻射的研究,多以平板邊界層為主,而矩形封閉體積的磁流體自然對流已有相當多的研究文獻,故本研究將針對磁流體在矩形封閉體積中受到一高溫壁面影響的自然對流,並分析熱輻射效應對流體速度及溫度分佈的影響。流場與溫度場的計算,採用SIMPLE演算法;另外,輻射熱通量則使用離散座標法求得。文中並分析磁場強度、浮力效應及長寬比對於磁流體自然對流的影響。 計算結果顯示磁場強度越強會抑制對流流動並降低熱通量;而熱輻射效應越強,則流體速度及熱通量越大,且流體的平均溫度越高;另外,當光學厚度越大時,則會因吸收效應而增加流體溫度,進而增加對流的效果;而散射比的結果顯示,散射對於熱通量較無影響,但散射比越大則會減少對流速度,這是由於吸收效應減少的結果。壁面放射率越大,很明顯的增加了熱輻射的傳遞,對於流體的速度及熱通量都有顯著的增加,但流體的平均溫度減少。在幾何外型上,較大的長寬比,其熱傳效果較差,但流體速度及平均溫度較高;而長寬比越小時,流體速度及熱通量增加,但流體的平均溫度減少。當浮力效應越大時,會造成流體對流速度、平均溫度及熱通量的增加。 Magnetohydrodynamics(MHD) has long been a subject of great importance. In some cases, radiative transfer may contribute to the flow and energy transfer. However, currently available literature on the boundary layer flows. The radiation effects on MHD in a rectangular enclosure have receive very few attention. This work investigates the radiative transfer effects on the natural convection of a magnetic fluid in a rectangular enclosure. The SIMPLE is used to solve the momentum and energy equations and the discrete ordinates method is employed to solve the radiative transfer equation. The results show that both the fluid movement and the heat flux are reduced with the application of a magnetic field. On the other hand, the radiation effects enhance the convection and heat transfer. As the optical thickness increases, the fluid temperature increases because more energy is absorbed. As a result, convection is enhanced while the scattering albedo has little effect on the heat flux, it reduces the fluid movement greatly. The boundary emissivity also affects the heat and fluid flows. As the emissivity increases, the radiative transfer increases, and hence the fluid flow and heat transfer increases. The aspect ration(height-to-width ratio) of the enclosing rectangle has effects on the energy and momentum transfer of the system. As the aspect ratio is increased, the heat flux on the high temperature surface decreases.
    Appears in Collections:[機械工程研究所] 博碩士論文

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