臺灣博碩士論文加值系統

本研究使用流體力學分析軟體Ansys Fluent分析立體漸擴微流道中的沸騰現象，以流體體積法計算，可直觀地於結果，觀察氣、液兩相於圓形、方形、六邊形截面之漸擴管中的分佈情形與生長狀況。定義固定之流道壁溫度、流道內壓力與工作流體質量流率，並設定氣泡生成參數、過熱度等條件，模擬漸擴管中之沸騰現象。同時比較不同截面形狀與之漸擴程度的漸擴管內之氣泡生長狀況，比較氣泡生長狀況、熱通量、頭尾端壓降，並探討各種設計的優缺點。
結果顯示在流道錐度為0至0.06範圍內，當錐度越大時，會導致熱通量呈現等差減少的趨勢，熱傳率則有逐漸上升的趨勢，而壓降則呈現等比減少的趨勢。若加大流率時，較大的流量能帶來更大的熱通量與總壓降，且能降低流道內總壓降的震盪幅度，並減少氣泡阻塞流道造成熱通量下降的狀況。
方形流道在低流量能避免氣泡阻塞，並且相較另外兩種造型有最低的流道入口壓降。最終，經過優化的方形漸擴流道相比平直的流道，在總壓降下降了64%的同時，熱傳率得到了17%提升。

This study uses fluid mechanics analysis software ANSYS FLUENT to analyze the boiling phenomenon in the three -dimensional gradual expansion tract. It is calculated based on the fluid volume method. The results can be intuitively observed. The distribution situation and growth status in tube expansion. Define the fixed runner wall temperature, the pressure in the flow channel, and the quality flow rate of the work fluid, and set the conditions of bubbles to generate parameters and over heat to simulate the boiling phenomenon in the gradual expansion of the tube. At the same time, the growth status of the bubbles in the tube in different section shapes and gradually expansion, compare the growth status, heat flux, head and tail pressure drop, and discuss the advantages and disadvantages of various design. Results showed that within the range of 0 to 0.06, when the taper, the larger, it would lead to a tendency to reduce the difference in heat flux. trend. If the current rate is increased, the larger flow can bring a greater thermal flux and total pressure drop, and can reduce the fluctuation amplitude of the total voltage drop in the flow tract, and reduce the bubble blocking the flow tract. situation. The square flow tract can avoid bubble obstruction at a low flow, and the lowest flowing inlet pressure is dropped compared to the other two shapes. In the end, the optimized square gradients were expanded by a straight runway, while the total voltage dropped by 64%, the thermal biography rate was increased by 17%.

摘　要 i
ABSTRACT ii
誌　謝 iv
目　錄 v
表　目　錄 viii
圖　目　錄 ix
第1章 緒論 1
1.1 前言 1
1.2 研究動機與目的 2
1.3 沸騰 3
1.3.1 沸騰種類 3
1.4 微流道 4
1.4.1 微流道的製造 4
1.5 文獻探討 5
第2章 控制方程式與數值方法 9
2.1 控制方程式 9
2.1.1 質量和動量守恆方程式 10
2.1.2 能量守恆方程式 11
2.2 數值方法 11
2.2.1 VOF流體體積法 11
2.2.2 相轉換方程式 13
2.3 通用傳輸方程式 16
2.3.1 有限差分法 16
2.3.2 有限元素法 17
2.3.3 有限體積法 17
2.4 空間離散格式 17
2.4.1 一階上風(First-Order Upwind Scheme) 17
2.4.2 二階上風(Second-Order Upwind Scheme) 18
2.5 壓力-速度耦合方法 18
2.5.1 SIMPLE 18
2.5.2 PISO法 21
第3章 模型與邊界條件 22
3.1 數值模型與網格 23
3.2 流體性質 25
3.3 邊界條件 26
第4章 結果與討論 27
4.1 理論驗證（Benchmark） 27
4.2 氣體體積分率(volume fraction of vapor) 28
4.3 熱通量(heat flux) 35
4.4 熱傳率(Heat transfer rate) 41
4.5 壓降(Pressure drops) 43
4.5.1 重力壓降 49
4.5.2 加速度壓降 54
4.5.3 摩擦壓降 59
第5章 結論與未來展望 64
5.1 結論 64
5.2 未來展望 66
參考文獻 67

[1] clearesult. (n.d.). What is the 80 PLUS specification. Retrieved May 24,2022,from https://www.clearesult.com/80plus/program-details#program-details-table
[2] wikipedia. (n.d.). Operating temperature.Retrieved May 24,2022,from https://en.wikipedia.org/wiki/Operating_temperature
[3] intel.(n.d.).CPU時脈速度Retrieved May 24,2022,from https://www.intel.com.tw/content/www/tw/zh/gaming/resources/cpu-clock-speed.html
[4] intel.(n.d.).超頻是甚麼?.Retrieved May 24,2022,from https://www.intel.com.tw/content/www/tw/zh/gaming/resources/how-to-overclock.html
[5] intel.(n.d.).什麼是散熱設計功率(TDP)?.Retrieved May 24,2022,fromhttps://www.intel.com.tw/content/www/tw/zh/support/articles/000055611/processors.html
[6] Yuji FURUKAWA, & Seiji HIRAI (1993). An Analysis of Anisotropic Etching Process.Etching toward Depth Direction. JSPE-58-0 2,92-02.283.
[7] ucdavis. (n.d.). Wet and Dry Etching. Retrieved May 24,2022,from https://www.ece.ucdavis.edu/~anayakpr/Papers/Wet%20and%20Dry%20Etching_submitted.pdf
[8] T.G. Karayiannis and M.M. Mahmoud, Flow boiling in microchannels: Fundamentals and applications, Applied Thermal Engineering, 115 (2017), 1372-1397.
[9] G. Liang and I. Mudawar, Review of channel flow boiling enhancement by surface modification, and instability suppression schemes, International Journal of Heat and Mass Transfer, 146 (2020), 118864.
[10] Moradikazerouni, A., Afrand, M., Alsarraf, J., Mahian, O., Wongwises, S., & Tran, M. D. (2019). Comparison of the effect of five different entrance channel shapes of a micro-channel heat sink in forced convection with application to cooling a supercomputer circuit board. Applied Thermal Engineering, 150, 1078-1089.
[11] Maselli, V., Osellame, R., Cerullo, G., Ramponi, R., Laporta, P., Magagnin, L., & Cavallotti, P. L. (2006). Fabrication of long microchannels with circular cross section using astigmatically shaped femtosecond laser pulses and chemical etching. Applied physics letters, 88(19), 191107.
[12] B. Dang, M. S. Bakir and J. D. Meindl, "Integrated thermal-fluidic I/O interconnects for an on-chip microchannel heat sink," in IEEE Electron Device Letters, vol. 27, no. 2, pp. 117-119, Feb. 2006, doi: 10.1109/LED.2005.862693.
[13] Lee, D. K., Kwon, J. Y., & Cho, Y. H. (2019). Fabrication of microfluidic channels with various cross-sectional shapes using anisotropic etching of Si and self-alignment. Applied Physics A, 125(5), 1-7.
[14] Alugoju, U. K., Dubey, S. K., & Javed, A. (2020). 3D Transient heat transfer analysis and flow visualization study in diverging microchannel for instability mitigated two-phase flow: A numerical study. International Journal of Heat and Mass Transfer, 160, 120212.
[15] J. Broughton and Y.K. Joshi, Flow boiling in geometrically modified microchannels, Physics of Fluids, 33 (2021), 103308.
[16] N. Tiwari, M.K. Moharana, Conjugate heat transfer analysis of liquid-vapor two-phase flow in a microtube: a numerical investigation, International Journal of Heat and Mass Transfer, 142 (2019), 118427.
[17] K. Tan, Y. Hu and Y. He, Effect of wettability on flow boiling heat transfer in a microtube, Case Studies in Thermal Engineering, 26 (2021), 101018.
[18] S.S. Bertsch, E.A. Groll and S.V. Garimella, A composite heat transfer correlation for saturated flow boiling in small channels, International Journal of Heat and Mass Transfer, 52 (2009), 2110-2118.
[19] Huang, S. C., Kawanami, O., Kawakami, K., Honda, I., Kawashima, Y., & Ohta, H. (2008). Experimental study of the relation between heat transfer and flow behavior in a single microtube. Microgravity Science and Technology, 20(3), 193-197.
[20] C.W. Hirt and B.D. Nichols, "Volume of Fluid (VOF) Method for the Dynamics of Free Boundary," Journal of Computational Physics, Vol. 39, 1981, pp.201-225.
[21] W.H. Lee, "A Pressure Iteration Scheme for Two-Phase Flow Modeling," in Multiphase Transport Fundamentals, Reactor Safety, Applications, T.N. Veziroğlu (Ed),Hemisphere Publishing Corporation, Vol. 1, 1980.
[22] D.Z. Guo, D.L. Sun, Z.Y. Li and W.Q. "Tao, Phase Change Heat Transfer Simulation for Boiling Bubbles Arising from a Vapor Film by VOSET Method," Numer. Heat Transfer A, Vol. 59, 2011, pp.857-881.
[23] S.W.J. Welch and J. Wilson, "A Volume of Fluid Based Method for Fluid Flows with Phase Change," J. Comput. Phys, Vol. 62, 2000, pp.662-682.
[24] Kull, H. J. (1991). Theory of the Rayleigh-Taylor instability. Physics reports, 206(5), 197-325.
[25] D. Sun, J. Xu and Q. Chen, "Modeling of the Evaporation and Condensation Phase-Change Problems with FLUENT," Numerical Heat Transfer, Part B : Fundamentals, Vol. 66, No. 4, 2014, pp.326-342.
[26] B.J. Kim, J.H. Lee and K.D. Kim, "Rayleigh–Taylor instability for thin viscous gas films: Application to critical heat flux and minimum film boiling," International Journal of Heat and Mass Transfer, Vol. 80, 2015, pp.150-158.
[27] B.E. Burk, T.P. Grumstrup, T.A. Bevis, J. Kotovsky, T.M. Bandhauer, Computational examination of two-phase microchannel heat transfer correlations wit conjugate heat spreading, Int. J. Heat Mass Transf. 132 (2019) 68–79.
[28] S.S. Bertsch, E.A. Groll, S.V. Garimella, A composite heat transfer correlation for saturated flow boiling in small channels, Int. J. Heat Mass Transf. 52 (7–8(2009) 2110–2118.
[29] J.C. Chen, Correlation for boiling heat transfer to saturated fluids in convective flow, I&EC Process Des. Dev. 5 (3) (1966) 322–329.
[30] M.G. Cooper, Heat flow rates in saturated nucleate pool boiling – a wide- ranging examination using reduced properties, Adv. Heat Transfer 16 (1984) 157–239.
[31] Yeo, I., & Lee, S. (2022). 2D computational investigation into transport phenomena of subcooled and saturated flow boiling in large length to diameter ratio micro-channel heat sinks. International Journal of Heat and Mass Transfer, 183, 122128.