Abstract    Electrohydrodynamic effect on natural convection in horizontal channels is investigated from a numerical point of view. The EHD effect is induced by narrow strip electrodes placed at the bottom wall of the channel. The channel is subjected in a first stage only to the electric forces, and in a second stage to the simultaneous action of a temperature gradient and an electric field. The interactions between electric field, flow field and temperature field are analyzed. It can be concluded that charge density distribution, flow pattern and temperature distribution are substantially affected by the arrangement of the electrodes; in fact four different arrangement were treated. The effect of pure electroconvection on charge density distribution and on flow pattern was studied. A periodic flow corresponding to particular values of electric Rayleigh was observed, then the impact of combined electro-thermo convection on heat transfer was undertaken in a second step and it was noted that the optimum arrangement of the electrodes provides an increase in heat transfer of up to 13%. The effect of the applied electric forces is also studied in order to highlight the importance of putting compromise between the supplied voltage and arrangement of the electrodes. Finally, a study of optimized configuration of electrodes was achieved.

Keywords    Heat transfer, Electro-Hydro-Dynamic, Electro-Thermo-Convection, Numerical simulation

چکیده    اثر الکتروهیدرودینامیکی (EHD) بر روی گرایش طبیعی در کانال­های افقی از دیدگاه عددی بررسی شده است. اثر EHD توسط الکترودهای نوار باریک قرار داده شده در دیوار پایین کانال ایجاد می­شود. کانال در مرحله اول تنها به نیروهای الکتریکی و در مرحله دوم به اثر همزمان یک گرادیان درجه حرارت و یک میدان الکتریکی اعمال می­شود. تعاملات بین میدان الکتریکی، میدان جریان و میدان دما تجزیه و تحلیل می­شود. می­توان چنین نتیجه گرفت که توزیع چگالی شار، الگوی جریان و توزیع دما به طور قابل ملاحظه­ای از آرایش الکترودها تأثیر می­پذیرند. در واقع، چهار روش مختلف الکترود تحت مطالعه قرار گرفتند. اثر الکتروشیمیایی خالص بر توزیع تراکم شارژ و الگوی جریان مطالعه شده است. یک جریان دوره­ای که مربوط به مقادیر ویژه الکتریکی رایلی بود، مشاهده شد. اثر ترکیب الکتریکی حرارتی در انتقال حرارت در مرحله دوم بررسی و مشاهده شد که ترتیب الکترودهای بهینه افزایش انتقال حرارت تا 13٪ را فراهم می­کند. اثر نیروهای الکتریکی اعمال شده نیز مورد توجه قرار گرفته است تا اهمیت مصالحه بین ولتاژ تامین شده و تنظیم الکترود را برجسته نماید. در نهایت، مطالعه پیکربندی الکترود بهینه شده به دست آمد.

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