結合強制脈衝流動與多孔熱沉用於電子元件之散熱增強分析

近代電子產品面臨微小化後散熱不易的嚴重問題，導致需要尋求一種更快速有效的散熱技術。本文目的嘗試結合多孔質熱沉與脈衝流兩種熱傳增強方法同時施加於發熱之矩形電子元件之對流熱傳中，探討其散熱增強之效益。研究方法為以數值模擬分析於強迫脈衝流下，兩平行管道內之三矩形發熱元件間插入多孔材料的熱流場分佈及其熱傳特性。文中純流體區內遵守unsteady Navier-Stoke方程式，多孔材質區內則因考慮多孔質微結構造成之邊界不滑移與慣性效應，故採用transient Forchheimer-Brinkman-Darcy模式模擬多孔質熱沉內部流動狀態。導入流線函數-渦度公式，將無因次化複合層熱流場系統方程式轉成為電腦可解的差分方程式。對於介面不連續處之物性則以調和平均公式處理，以確保參數之連續性。藉由變化各項參數，包括達西數Da、頻率參數St、振幅參數A、雷諾數Re、熱源間隔以及多孔材料之與值，用以探討熱流場變化及其對熱傳增強效益。經數值模擬結果顯示，由脈衝流場與多孔質所引發位於兩熱源體間與下游之循環渦流的週期性結構變化，對第二塊以下之熱源體之對流散熱有增強的效益，且此散熱增強的效益會隨著達西數、脈衝頻率、脈衝振幅、雷諾數及熱傳導率等增加而增加，但隨多孔質高度的增加而減少。

關鍵字

脈衝流；多孔質熱沉；熱傳增強

並列摘要

Modern microelectronics thermal management is facing considerable challenges in the wake of miniaturizing of components leading to higher demands on net heat flux dissipation. The main motivation of this study is to explore the effects of both the heat transfer enhancement factors by flow pulsation and porous-cover heat sink on the convective cooling of electronic device. The present work presents a numerical study of heat transfer enhancement by forced pulsating convection at the vertical walls of heat generating blocks evenly mounted on the lower plate of a channel through the insertion of porous materials between the blocks. The flow over the fluid region is governed by the unsteady Navier-Stokes equation, and the flow through the porous medium is governed by the transient Darcy-Brinkman-Forchheimer equation that account for the effects of the impermeable boundary and inertia. Through the use of a stream function-vorticity transformation, solution of the coupled governing equations for the porous/fluid composite system is obtained using the control-volume method. The harmonic mean formulation was used to handle the discontinuous thermophysical properties across the interface. In addition, the dependence of streamline, isotherm, and enhanced heat transfer rate on the governing parameters defining the problem is examined in detail. The results show that the periodic alteration in the structure of recirculation flows inside the inter-block region and the downstream block, caused by both porous block and flow pulsating, significantly enhances the heat transfer rate on the second and subsequent heat blocks. This cooling enhancement increases with the Darcy number Da, Reynolds number Re, pulsation amplitude A and frequent St, and conductivity ratio , but decreases with the thickness of porous insert Hp*.

並列關鍵字

Pulsating flow ； Porous heat sink ； Heat transfer enhancement

參考文獻

[3] J. Brinkman, C., “A Calculation of the Viscous Force Exerted by a Flowing Fluid on a Dense Swarm of Particles,” Applied Science Research, Al.: pp. 27-34, 1947.

[4] K. Vafai, and C. L. Tien, “Boundary and Inertial Effects on Flow and Heat Transfer in Porous Media”, Int. J. Heat Mass Transfer Vol. 24, 195-203, 1981.

[5] K. Vafai, and C. L. Tien, “Boundary and Inertial Effects on Convection Mass Transfer in Porous Media”, Int. J. Heat Mass Transfer Vol. 25, 1183-1190, 1982.

[6] M. L. Hunt, and C. L. Tien, “Effects of Thermal Dispersion on Forced Convection in Fibrous Media,” Int. J. Heat Mass Transfer, Vol. 31, pp. 301-309, 1988.

[7] M. Kaviany, “Laminar Flow through a Porous Channel Bounded by Isothermal Parallel Plates,” Int. J. Heat Mass Transfer, Vol. 28, pp.851-858, 1985.

國際替代計量

結合強制脈衝流動與多孔熱沉用於電子元件之散熱增強分析

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