平板型迴路式熱管散熱之研究

The Thermal Performance Investigation of Loop Heat Pipe with Plate Evaporator

陳志嘉(Zhi-Jia Chen)

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.2007.00453

摘要

迴路式熱管(Loop Heat Pipe)具有高熱傳量、傳輸距離遠等優點，有相當大的潛力應用在電子散熱。一般圓管型迴路式熱管必須加裝鞍部(saddle)才能應用於散熱平面上，由於加裝鞍部會使得熱阻增加而影響性能，因此平板式蒸發器可改善加裝鞍部之缺點。由文獻得知平板式迴路式熱管其熱洩漏(Heat leak)問題比圓管型迴路式熱管更為嚴重，而使得在啟動困難度更高且熱阻亦較高。因此本文利用了不鏽鋼網及單層與雙層主毛細結構之應用，實驗結果發現，平板式迴路式熱管加上不鏽鋼網之應用且當有雙層主毛細結構時，可有效降低熱洩漏之影響，在低瓦數啟動及運作上更為順利。另外將蒸汽段液體管路管徑由3mm改成4mm，蒸汽流動阻力降了約四倍之多，可增加熱傳量。在熱源溫度不超過100℃、熱沉溫度30℃的情況下，水平狀態下操作可達140W，垂直狀態下可達170W。

關鍵字

迴路式熱管 ； 平板型蒸發器 ； 熱洩漏

並列摘要

Loop Heat Pipes (LHPs), which are generally and widely used with cylindrical evaporators, have a great potential for applications on spacecrafts and electronic cooling due to the advantages of high transfer capacity and long transport distances. However, the cylindrical evaporators of loop heat pipes cannot work on a flat thermo-contact surface without saddle. The saddle creates an extra thermal resistance. To avoid the above disadvantages, we utilize the flat evaporators of loop heat pipes. According to the literature, however, the heat leak problem is more serious in the flat evaporators than in the cylindrical evaporators. This problem also makes more difficult start-up and higher thermal resistance of flat evaporators. Hence this study uses stainless steel mesh and compares the affect of one or two primary wick structure. The results show that that method can ease heat leak problem, when flat evaporators of loop heat pipes have stainless steel mesh and two primary wick structures. Then loop heat pipes can start-up and work more easily at low load. Vapor flow resistance drops by four times and increases heat transfer when diameter of vapor line increases from 3mm to 4mm. When the temperature of the heater is less than 100 oC and the sink temperature is at 30oC, the maximum heat capacity reaches 140W for horizontal orientation and 170W for vertical orientation.

並列關鍵字

loop heat pipe ； flat evaporator ； heat leak

參考文獻

【3】Wolf et al., 1994, “Loop Heat Pipes-their Performance and Potential” SAE paper 941575.

【4】J.T. Dickey, G.P. Peterson, 1994, “Experimental and Analytical Investigation of a Capillary Pumped Loop”Journal of Thermophysics and Heat Transfer Vol.8 No.3 July-Sept.

【5】Maidanik, Y.F., 1994, “Design and Investigation of Methods of Regulation of Loop Heat Pipes for Terrestrial and Space Applications”, Institute of Thermodynamics. Ural Division of the Russian Academy of Sciences, SAE Technical Paper 941407.

【6】Kiseev, V.V. et al., 1997, “Development of Two-phase Loops with Capillary Pumps” SAE Paper 972482.

【8】V.G.Pastukhov et al., 1999, “Development and Investigation of Miniature Loop Heat Pipes”, SAE Paper 1999-01-1983.