鰭片底面裝置針狀電極之EHD增強散熱技術研究

EHD Enhanced Heat Transfer by Inserting Needle Electrodes into Heat Sink

張兆秋(Chao-Chiu Chang)

指導教授 ： 許文震

國立清華大學/工學院/動力機械工程學系/碩士(2007年)

https://doi.org/10.6843/NTHU.2007.00452

摘要

在無法使用動件的散熱系統中，被動式的自然對流散熱能力已不敷使用，因此本研究主要是探討使用無動件的EHD (electrohydrodynamics)技術來改善自然對流下的散熱能力，將電極嵌入至鰭片內，以EHD所產生的電暈風搭配鰭片因溫差所產生的浮力，來加強鰭片的散熱能力。在本文中探討的參數有電場極性、電極與鰭片間距、鰭狀物高度、鰭狀物幾何形狀、鰭狀物相互間的距離與電極排列位置，負電暈的火花放電電壓較高電暈風強度較強，因此無論何種條件下散熱效果均優於正電暈。 EHD技術屬於強制對流因此在鰭片設計上，有效的增加散熱面積反而能降低對流熱阻。在本實驗中，鰭狀物高度1cm時，EHD可有效的擾動降低對流熱阻，熱對流係數最高可增強至自然對流下的3.5倍，而對流熱阻最低可降低至自然對流下的一半，此外，將電極嵌入至鰭片內可大幅降低消耗瓦數，提升散熱效率。

關鍵字

電液動力學 ； 電暈風 ； 熱對流係數增強

並列摘要

It is not suitable for the rate of heat transfer under natural convection in some situations which can not utilize active cooling technology, so heat transfer enhanced by electrohydrodynamics (EHD) is experimentally investigated in this work. The system of inserting needle electrodes into heat sink can effectively increase the rate of heat transfer due to the corona wind generated by EHD. The polarity of electric field, distance of electrode to pin-fin, height of pin-fin, configuration of pin-fin, spread of pin-fin and position of electrode will be taken into account. The results reveal that both the spark voltage and heat transfer rate for negative corona are better than those for positive one. In pin-fin design, EHD technology belongs to force convection for reducing thermal resistance of convection with increasing area of cooling. When height of pin-fin is one centimeter, EHD can distort flow field reduced thermal resistance of convection. The maximum heat transfer coefficient with EHD is greater than that without EHD by three and half times. The minimum thermal resistance of convection with EHD is lower than that without EHD by half times. In addition to, inserting needle electrodes into heat sink is not only reduced power consumption but also improved efficiency.

並列關鍵字

electrohydrodynamics ； corona wind ； enhanced convection

參考文獻

2.Robinson, M., “Movement of Air in the Electric Wind of the Corona Discharge,” Transactions of the American Institute of Electrical Engineers, V. 80, pp. 143-150 (1961).

3.Steven C. Goheen, Kari Gaither, Shantha M. Anantatmula, Gary M. Mong, Lyle B. Sasser, and Delbert Lessor, “Corona Discharge Influences Ozone Concentrations Near Rats,” Bioelectromagnetics, V. 25, pp. 107-113 (2004).

4.Hauksbee, F., “Physico-Mechnical Experiments on Various Subjects,” 1st ed., London, pp. 46-47 (1719).

5.O’Brien, R. J. and A. J. Shine, “Some Effects of an Electric Field on Heat Transfer From a Vertical Plate in Free Convection,” Journal of Heat Transfer, V. 89, pp. 114-116 (1967).

7.Mitchell, A. S. and L. E. Williams, “Heat Transfer by the Corona Wind Impinging on a Plate Surface,” Journal of Electrostatics, V. 5, pp. 309-324 (1978).