鋁質蒸汽腔體均熱片之製造與分析

Fabrication and Analysis of Aluminum Vapor Chamber Heat Spreaders

洪裕勛(Yu-Hsun Hung)

指導教授 ： 康尚文

淡江大學/工學院/機械與機電工程學系博士班/博士(2009年)

https://doi.org/10.6846/TKU.2009.00611

摘要

本研究主要是針對鋁質蒸汽腔體均熱片之製造與分析，文中分為鋁質蒸汽腔體的實驗分析與二相流分析應用於蒸汽腔體。蒸汽腔體外觀尺寸58mmx58mmx6mm，使用鋁合金6061作為材料，毛細結構採用向中心傾斜的放射狀溝槽以及鋁粉燒結結構兩種設計。溝槽的尺寸分別是寬度0.4mm與深度0.65-0.91mm；鋁粉燒結毛細結構孔隙率為0.32，厚度為0.5mm，並設計八支直徑3mm燒結柱。工作流體採用丙酮充填兩種鋁質蒸汽腔體。
在鋁質蒸汽腔體的研究部分，實驗測試包含最佳充填量、隨著功率變化的整體熱阻值、以及散熱端表面溫度的量測。結果顯示放射狀溝槽式鋁質蒸汽腔體最佳充填率為25%，並藉由表面溫度的結果得知溝槽毛細結構可提升整體熱傳性能的特性。燒結式鋁質蒸汽腔體最佳充填率為55%；隨著功率的變動，整體熱阻值的變動(0.65-0.69℃/W)小於溝槽式的設計(0.72-0.91℃/W)。
本文第二部份為探討二相流分析應用於蒸汽腔體的研究。運算分析使用計算流體力學模擬軟體Fluent中的多相流模組-VOF來研究工作流體於蒸汽腔體中的作動情形。文中利用汽液相、溫度與速度分佈圖來進行分析與研究。蒸汽腔體尺寸比照文獻設計為46.5mmx4.6mm的二維軸對稱模型。結果探討包含啟動機制與達到穩態的工作流體汽相、液相、溫度場、速度場運作過程。另針對毛細結構支柱與多點熱源作模擬分析。
模擬分析比對文獻實驗數據與數值分析，結果顯示蒸汽腔體底部中心溫度略高於實驗與數值分析，與實驗數據僅差距1℃。並藉由啟動至穩態的模擬分析，探討工作流體汽相、液相、溫度場與速度場變化的現象。隨著功率的輸入，工作流體逐漸產生相變化傳熱機制，並生成汽泡、蒸汽膜。文中並探討毛細支柱的設計與多熱源的關係。透過模擬的結果顯示出，理想的狀況之下，毛細支柱的設計與否，對於蒸汽腔體熱傳效率影響並不明顯。

關鍵字

蒸汽腔體 ； 鋁 ； 鋁合金 ； 燒結 ； 二相流 ； Fluent ； VOF

並列摘要

This study presents the fabrication and analysis of aluminum vapor chamber heat spreaders. It is divided into two main topics, fabrication and experiment of aluminum vapor chamber and the two-phase flow analysis inside the vapor chamber, respectively. Aluminum alloy 6061 as the container material is used to fabricate the aluminum vapor chamber with the radial grooved wick and sintered aluminum powders wick. Two kinds of aluminum vapor chambers are of the same dimension of 58mmx58mmx6mm. For radial grooved aluminum vapor chamber, the groove is dimension 0.4mm wide and 0.65-0.91mm deep due to an arc design and the radius of central pool is 10.16mm. For sintered aluminum powders vapor chamber, the sintered wick is 0.5mm thick and eight pillars with diameter of 3mm are inserted inside it. The porosity is 0.32. The working fluid is acetone charged with all aluminum vapor chambers.
The results of all aluminum vapor chambers present the optimum charging amounts of the working fluid and the overall thermal resistance with heat input power 20-80W in increment of 20W, as well as the temperature at the bottom of heat sink. According to measuring the charging amounts of the working fluid, the fill ratios of grooved and sintered vapor chamber are 25%(1.02g) and 55%(2.69g) respectively. These results show that the radial grooved wick structures enhance the heat transfer coefficient of vapor chamber due to heat conduction and phase change. Compared with two kinds of wick designs, the overall thermal resistance of sintered aluminum powders vapor chamber (0.65-0.69℃/W) is changed and less than one of radial grooved vapor chamber (0.72-0.91℃/W) after steady state with heat input power 20-80W in increments of 20W.
The second topic of this study is the two-phase flow analysis inside the vapor chamber. The two-phase flow analysis is done by Volume of Fluid (VOF) multi-flow method of CFD simulation software Fluent. The simulation model of vapor chamber is axisymmetrically two-dimensional model of 46.5mmx4.6mm followed Y. Koito’s literatures. The start-up operation of vapor chamber for the two-phase flow analysis and three kinds of Types for vapor chamber subjected to multiple discrete heat sources and effect of pillar design are discussed. The phase, temperature, velocity distributions are investigated.
The temperature at the center of the bottom of the vapor chamber for simulation result is in good agreement with the experimental and numerical of literature result, although the temperature of numerical result is slightly lower than simulation result. The start-up operation of vapor chamber is illustrated and discussed until steady state or dry out by the phase, temperature, and velocity distribution. With heat input power, the liquid phase is transferred to the vapor phase, and the bubbles or vapor films are formed. The phase change causes the significant temperature difference. The bubble growing leads to the velocity vortex. The velocity at the wick region is slighter than it at the vapor core. Vapor chamber with pillar design and subjected to multiple discrete heat sources are simulated and discussed with respect to different the phase, temperature, and velocity distribution. From simulation results, the top surface temperature distributions at the top wall with pillar design are somewhat the same as the temperature field with none pillar design. The pillar design does not affect the heat transfer efficiency of vapor chamber for ideal heat transfer of phase change.

並列關鍵字

Vapor chamber ； Aluminum ； Aluminum alloy ； Sintered powders ； Two-phase flow ； Fluent ； VOF

參考文獻

3. K. Take, Y. Furukawa, S. Ushioda, “Fundamental Investigation of Roll Bond Heat Pipe as Heat Spreader Plate for Notebook Computers,” IEEE Transactiona on Components and Packaging Technologies, Vol. 23, No. 1, pp. 80-85, 2000.

5. Y. Cao, M. Cao, “Wickless Network Heat Pipes for High Heat Flux Spreading Applications,” International Journal of Heat and Mass Transfer, Vol. 45, pp. 2539-2547, 2002.

6. L. F. Mondolfo, Aluminum Alloys: Structure & Properties, Butterworths, London, 1976.

7. S. W. Kang, S. H. Tsai, H. C. Chen, “Fabrication and Test of Radial Grooved Micro Heat Pipes,” Applied Thermal Engineering, Vol. 22, pp. 1559-1568, 2002.

8. S. W. Kang, S. H. Tsai, M. H. Ko, “Metallic Micro Heat Pipe Heat Spreader Fabrication,” Applied Thermal Engineering, Vol. 24, pp. 299-309, 2004.