本文以實驗方式，先調製出水基底相變化奈米乳液並測定其熱物性質後，針對以相變化奈米乳液取代純水為工作流體探討其於等熱通量加熱圓管內層流強制對流熱傳遞特性與效益。實驗中所用的圓管為銅管，其尺寸為:長度1300mm，外徑4.0mm，內徑3.4mm；其外管壁藉纏繞鎳鉻電阻線方式建構等熱通量加熱條件。本文所探討的相關參數包括進口溫度設定為27∘C，進口流量為12.5〖cm〗^3/min、24〖cm〗^3/min、60〖cm〗^3/min、120〖cm〗^3/min、180〖cm〗^3/min，加熱功率為20W、30W、40W、50W、60W，奈米乳液內含相變化材料質量分率為ωpcm= 1%、2%、5%、10%。本研究所得實驗量測結果顯示，在適當管內流量與管壁加熱量條件下，奈米乳液可隨其內含相變化材料質量分率提高而有效抑制加熱段壁溫，導致其局部強制對流熱傳係數相較於純水之最大增益值可達22%；同時，其有效黏度隨其內含相變化材料質量分率上昇，致使其管流壓降相較於水呈現劇增趨勢，最高可達2.2倍。

In this study, the water-based nano-PCM emulsions are prepared and their thermal physical properties are measured. The laminar forced convection heat transfer characteristics of using the water-based nano-PCM emulsions as the working fluid instead of water in a horizontal circular tube partially heated with constant heat flux have been investigated experimentally. A circular oxygen-free copper tube, for which the inner and outer diameters are 3.4 mm and 4.0 mm, respectively, is fabricated with an iso-flux heated section of length 40 cm. Forced convection heat transfer experiments have been performed for the horizontal tube using the pure water, the water-based nano-PCM emulsions containing various mass fractions of PCM particles (pcm = 1, 2, 5and 10%) as the heat transfer fluid under the following operating conditions: the volume flow rate Q = 12.5 ~ 180 cm3/min (the Reynolds number Rebf = 91 ~ 1325), the heating power applied at the outer wall of the tube qo = 20, 30, 40, 50, 60 W, and the inlet fluid temperature Tin near 27∘C. The results show that when the flow rate and the heat flux are in an appropriate ranges, the wall temperature of the iso-flux heated section can be effectively suppressed with increasing mass fraction of the nano-PCM emulsions, hence leading to an enhancement up to 22% in the local heat transfer coefficient compared with that of the pure water. Meanwhile, a penalty of pressure drop increase of using the nano-PCM emulsion to replace the pure water in the tube was found to uplift with the PCM mass fraction up to about 2.2 times.

參考文獻
[1] S.U.S. Choi, "Enhancing thermal conductivity of fluids with nanoparticles", in: D.A. Siginer, H.P. Wang, (Eds.), Developments and Applications of Non-Newtonian Flows, ASME, New York, FED-Vol. 231/MD-Vol. 66, pp. 99–105, 1995
[2] S. M. Jafari, Y. H. He, and B. Bhandari, "Nano-emulsion production by sonication and microfluidization - A comparison," International Journal of Food Properties, vol. 9, pp. 475-485, 2006.
[3] S. Kentish, T. J. Wooster, A. Ashokkumar, S. Balachandran, R. Mawson, and L. Simons, "The use of ultrasonics for nanoemulsion preparation," Innovative Food Science & Emerging Technologies, vol. 9, pp. 170-175, 2008.
[4] T. Delmas, H. Piraux, A. C. Couffin, I. Texier, F. Vinet, P. Poulin, et al., "How To Prepare and Stabilize Very Small Nanoemulsions," Langmuir, vol. 27, pp. 1683-1692, 2011.
[5] C. Qian and D. J. McClements, "Formation of nanoemulsions stabilized by model food-grade emulsifiers using high-pressure homogenization: Factors affecting particle size," Food Hydrocolloids, vol. 25, pp. 1000-1008, 2011.
[6] P. Fernandez, V. Andre, J. Rieger, and A. Kuhnle, "Nano-emulsion formation by emulsion phase inversion," Colloids and Surfaces a-Physicochemical and Engineering Aspects, vol. 251, pp. 53-58, 2004.
[7] L. J. Wang, X. F. Li, G. Y. Zhang, J. F. Dong, and J. Eastoe, "Oil-in-water nanoemulsions for pesticide formulations," Journal of Colloid and Interface Science, vol. 314, pp. 230-235, 2007.
[8] L. C. Peng, C. H. Liu, C. C. Kwan, and K. F. Huang, "Optimization of water-in-oil nanoemulsions by mixed surfactants," Colloids and Surfaces A-Physicochemical and Engineering Aspects, vol. 370, pp. 136-142, 2010.
[9] I. Sole, C. Solans, A. Maestro, C. Gonzalez, and J. M. Gutierrez, "Study of nano-emulsion formation by dilution of microemulsions," Journal of Colloid and Interface Science, vol. 376, pp. 133-139, 2012.
[10] B. Yang and Z. H. Han, "Thermal conductivity enhancement in water-in-FC72 nanoemulsion fluids," Applied Physics Letters, vol. 88, 2006.
[11] M. Chiesa, "Thermal conductivity and viscosity of water-in-oil nanoemulsions," Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 326 pp. 67–72, 2008.
[12] J. Xu, "Thermal conductivity and viscosity of self-assembled alcohol/polyalphaolefin nanoemulsion fluids," Nanoscale Research Letters, vol. 6, p. 274-???, 2011.
[13] Z. H. Han, F. Y. Cao, and B. Yang, "Synthesis and thermal characterization of phase-changeable indium/polyalphaolefin nanofluids," Applied Physics Letters, vol. 92, pp.????, 2008.
[14] H. Y. Sul, J. Y. Jung, and T. Kang, "Thermal conductivity enhancement of binary nanoemulsion (O/S) for absorption application," International Journal of Heat and Mass Transfer, vol. 54, pp. 1649-1653, 2011.
[15] P. Charunyakorn, S. Sengupta, and S. K. Roy, "Forced-convection heat-transfer in microencapsulated phase-change material slurries - flow in circular ducts," International Journal of Heat and Mass Transfer, vol. 34, pp. 819-833, 1991.
[16] M. Goel, S. K. Roy, and S. Sengupta, "Laminar forced-convection heat-transfer in microcapsulated phase-change material suspensions," International Journal of Heat and Mass Transfer, vol. 37, pp. 593-604, 1994.
[17] Y. W. Zhang and A. Faghri, "Analysis of forced-convection heat-transfer in microencapsulated phase-change material suspensions," Journal of Thermophysics and Heat Transfer, vol. 9, pp. 727-732, 1995.
[18] S. K. Roy and B. L. Avanic, "Laminar forced convection heat transfer with phase change material suspensions," International Communications in Heat and Mass Transfer, vol. 28, pp. 895-904, 2001.
[19] X. X. Hu and Y. P. Zhang, "Novel insight and numerical analysis of convective heat transfer enhancement with microencapsulated phase change material slurries: laminar flow in a circular tube with constant heat flux," International Journal of Heat and Mass Transfer, vol. 45, pp. 3163-3172, 2002.
[20] Z. N. Zhao, R. Hao, and Y. Q. Shi, "Parametric analysis of enhanced heat transfer for laminar flow of microencapsulated phase change suspension in a circular tube with constant wall temperature," Heat Transfer Engineering, vol. 29, pp. 97-106, 2008.
[21] R. L. Zeng, X. Wang, B. J. Chen, Y. P. Zhang, J. L. Niu, X. C. Wang, et al., "Heat transfer characteristics of microencapsulated phase change material slurry in laminar flow under constant heat flux," Applied Energy, vol. 86, pp. 2661-2670, 2009.
[22] Y. Yamagishi, H. Takeuchi, A. T. Pyatenko, and N. Kayukawa, "Characteristics of microencapsulated PCM slurry as a heat-transfer fluid," AICHE Journal, vol. 45, pp. 696-707, 1999.
[23] C. J. Ho, J. F. Lin, and S. Y. Chiu, "Heat transfer of solid-liquid phase-change material suspensions in circular pipes: Effects of wall conduction," Numerical Heat Transfer Part A-Applications, vol. 45, pp. 171-190, 2004.
[24] X. C. Wang, J. L. Niu, Y. Li, X. Wang, B. J. Chen, R. L. Zeng, et al., "Flow and heat transfer behaviors of phase change material slurries in a horizontal circular tube," International Journal of Heat and Mass Transfer, vol. 50, pp. 2480-2491, 2007.
[25] C. J. Ho, J. B. Huang, P. S. Tsai, and Y. M. Yang, "Preparation and properties of hybrid water-based suspension of Al2O3 nanoparticles and MEPCM particles as functional forced convection fluid," International Communications in Heat and Mass Transfer, vol. 37, pp. 490-494, 2010.
[26] C. J. Ho, J. B. Huang, P. S. Tsai, and Y. M. Yang, "On laminar convective cooling performance of hybrid water-based suspensions of Al2O3 nanoparticles and MEPCM particles in a circular tube," International Journal of Heat and Mass Transfer, vol. 54, pp. 2397-2407, 2011.
[27] S. K. Roy and B. L. Avanic, "Laminar forced convection heat transfer with phase change material emulsions," International Communications in Heat and Mass Transfer, vol. 24, pp. 653-662, 1997.
[28] 黃俊博, " 一水平圓管內PCM微粒/奈米微粒懸浮流體之熱發展強制對流熱傳特性研究, ” 國立成功大學機械工程研究所碩士論文，2008。
[29] 王景宏, ”相變化材料次微米膠囊製備與相關物性之研究“， 國立成功大學機械工程研究所碩士論文， 2009。