本研究以 STAR-CD 套裝軟體為計算平台,模擬三維冷卻渠道在不同雷諾數
,隨著往復式運動並考慮自然對流的條件下,探討流場的變化,及比較熱傳效
。此模擬並與實驗做同步對照,以驗證模擬的真實性,經模擬結果並結合前述 章節之內容可獲得以下結論:
1. 渠道在靜止或是振動時,熱傳效益隨著流體雷諾數增加。除了在 Re=150 時熱傳效益不受振動頻率增加而增加,其餘的 Re 下皆會隨著振動頻率增 加,整體熱傳效益也會隨之增加。
2. ㄇ型渠道在靜止或是振動的情況下,熱傳效益皆是前段加熱區熱傳效率最 好、中段加熱區次之,後段加熱區最差。
3. 當渠道振動時,在 下
益 各
1 週期時因為渠道向下,使得渠道內體積增加,為了4 補充多出的體積而導致流體有回吸的現象,此現象使得流體加熱時間增 加,熱傳效益因此較差。在
3 週期時,此時渠道正往上,因為相對速度4 的關係使得冷卻流體衝擊壁面的力量增強,且渠道幾何形狀改變,導致流 體加速,而使帶走熱量的速率增加,所以此時熱傳效率最好。
4. 當渠道振動時,後段加熱區因為迴流受到渠道振動時的破壞,使得囤積的 熱量被打散,所以在任何週期時,後段加熱區之熱傳效益普遍比靜態時佳。
5. 當渠道在振動時,熱傳效率相對於靜止時改善許多,本模擬最大整體 Nu 增 加率可達 56.6%。
6. ㄇ型渠道在作往復運動時,在各週期流場變化極為相似, Nu 會產生類似 的週期性變化。
參考文獻
1. P. P. Grassmann, and M. Tuma, “Applications of the Electrolytic Method-Ⅱ.
Mass Transfer within a Tube for Steady, Oscillating and Pulsating
Flows,”International Journal of Heat and Mass Transfer, Vol. 22, pp. 799-804, 1979.
un, “Heat Transfer in the Thermally
6, 1993.
in Tubes with Repeated-Rib Roughness,” International Journal of Heat and Mass Transfer, Vol. 14, No. 4, pp. 601-617, 1971.
4. A. T. Patera ,and B.B. Mikic, “Exploiting Hydrodynamic Instabilities Resonant
for Predicting the Momentum and Heat
Heat Transfer, Vol. 97, No. 2, pp. 249-267, 1975.
A. E. Bergles, “Recent Development in Convective Heat-Transfer Augmentation,” Applied Mechanics Reviews, vol.26, pp.675-682, 1973.
A. E. Bergles, “Survey And Evaluation of Techniques to Augment Convective 2. S. Y. Kim, B. H. Kang, and A. E. Hy
Developing Region of a Pulsating Channel Flow,” International Journal of Heat and Mass Transfer, Vol. 36, No. 17, pp. 1257-126
3. A. E. Bergles, “Heat Transfer Enhancement – The Encouragement and Friction
Heat Transfer Enhancement,”International Journal of Heat and Mass Transfer, Vol. 29, No. 8,pp. 1127-1138, 1986.
5. R. L. Webb, E. R. G. Eckert, and R. J. Goldstein, “Heat Transfer and Friction in Tubes with Repeated-Rib Roughness,” International Journal of Heat and Mass Transfer, Vol. 14, No. 4,pp. 601-617, 1971.
6. M. J. Lewis, “An Elementary Analysis
Transfer Characteristics of a Hydraulically Rough Surface,” ASME Journal of
7.
8.
9. A. E. Bergles and R. L. Webb, the Literature on Convective Heat Transfer Augmentation,” Advances in Enhanced Heat Transfer-1985, S. M.
o
ite ughed Walls,” ASME Journal of Heat Transfer, Vol. 106, pp. 774-781,
hanced Heat Transfer,
Piston Cooling in Marine Diesel
a ravity Open Thermosyphon,” International
a al Journal of Heat and Mass Transfer “A Guide to
Shenkman, J. E. O’Brien, I. S. Habib, and J. A. Kohler, Vol. HTD-V l.43, pp.81-90, ASME Symposium, 1985.
10. J. C. Han, “Heat Transfer and Friction in Channels with Two Oppos Rib-Ro
1984.
11. Y. Park, J. Cha, and M. Kim, “Heat Transfer Augementation Characteristics of Various Inserts in a Heat Exchanger Tube,” Journal of En
Vol.7,pp.23-33,2000.
12. S. W. Chang and L. M. Su, “Influence of Reciprocating Motion on Heat Transfer Inside a Ribbed Duct with Application to
Engines,” Journal of Ship Research, Vol. 41, No. 4, pp. 332-339,1997.
13. S. W. Chang, L. M. Su, W. D. Morris, and T. M. Liou, “Heat Transfer in Smooth-Walled Reciprocating Anti-G
Journal of Heat and Mass Transfer, Vol. 42, pp. 1089-1103, 2003.
14. Wu-Shung Fu, Wen-Wang Ke, Ke-Nan Wang, “Laminar Forced Convection in Channel With a Moving Block,” Internation
Vol. 44(13), pp.2385-2394, 2001.
15. 賴昱志,"增進活塞熱傳效益之數值模擬", 國立交通大學機械工程研究 所碩士論文,2004。
16. 連信宏,"利用多孔性介質增強活塞頂面之熱傳效率", 國立交通大學機 械工程學系碩士論文,2005。
17. 劉維元,"多孔性介質的熱傳分析", 國立交通大學機械工程研究所碩士 論文,1994。
18. 黃新鉗,"加裝多孔凸塊以增強熱傳效率之研究", 國立交通大學機械工 程研究所博士論文,1997。
19. 余政倫,"往復式冷卻渠道之熱流實驗", 國立交通大學機械工程學系碩 士論文,2006。
20. 陳沅佑,"實驗探討ㄇ型振動管之熱傳現象", 國立交通大學機械工程學 系碩士論文,2007。