本研究係以實驗方式量測充填奈米流體方型容器自然對流平均熱傳係數；容器內左/右直立壁分別為加熱/冷卻等溫壁面，其餘邊壁皆為絕熱壁。本實驗係以氧化鋁 (Al2O3) 奈米微粒分別離散於水及乙二醇調製成不同之奈米流體；調製過程發現，藉改變溶液pH值 (= 3)，可提升奈米微粒懸浮於基底流體之穩定度。針對所調製成之奈米流體，進而實驗測定其相關熱物理性質，諸如懸浮微粒粒徑大小分佈、密度、黏滯係數、熱傳導係數等，隨溫度與微粒濃度變化情形。容器內奈米流體自然對流熱傳實驗所探討參數範圍則為：萊利數，RaT,b = 10E6~10E8；奈米微粒質量濃度，Cm =0.35%、1%、3.52%、6.86%、10.04%。由量測所得容器加熱壁面平均熱傳係數之結果顯示，於水或乙二醇等基底流體內離散低濃度奈米微粒 (Cm = 0.35%) 確可提升容器內自然對流熱傳遞率。

　　In the present study, surface-averaged heat transfer coefficient for natural convection in a square enclosure filled with nanofluids has been determined experimentally. The enclosure is heated differentially across the two vertical isothermal walls, while the other side-walls are assumed adiabatic. The nanofluids considered were prepared by dispersed various amount of alumina (Al2O3) nanoparticles in water or ethylene glycol as the base fluid. In preparing the nanofluids, it was observed that stable suspension of the nanoparticles in the base fluids can be achieved by adjusting properly the pH values of the nanofluids (pH = 3). In addition, thermophysical properties of the nanofluids prepared including the particle size, the density, viscosity, and thermal conductivity, were measured as a function of temperature as well as the mass fraction of the nanoparticles. The heat transfer experiments for natural convection in the enclosure have been undertaken for the relevant parameters in the following range：Rayleigh number, RaT,b = 10E6~10E8,the mass fraction of nanoparticles Cm =0.35%、1%、3.52%、6.86%、10.04%. The results obtained for the averaged heat transfer coefficient over the isothermally heated wall reveal that enhancement in the natural convection heat transfer across the enclosure does arise markedly by dispersing small mass fraction of alumina nanoparticles (Cm = 0.35%) in water or ethylene glycol.

Choi, S. U. S., 1995 “Enhancing Thermal Conductivity of Fluids with Nanoparticles”, Developments and Applications of Non-Newtonian Flows, Siginer DA, Wang HP (eds) FED vol. 231/MD-vol. 66, ASME, New York, pp 99-105.
Choi, S. U .S., Eastman, J. A., Li, S., Yu, W., Thompson, L. J., 1999 “Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles”, Applied Physics Letters, Vol. 78, No.6, pp 474-480.
Choi, S. U .S., Wang, X., Xu, X., 2001 “Thermal Conductivity of Nanoparticle-F;uid Mixture”, Journal of Thermophysics and Heat Transfer, Vol. 13 pp 718-720.
Das, S. K., Putra, N., Thiesen, P., Wilfried, R., 2003 “Temperature Dependence of Thermal Conductivity Enhancement for Nanofluids”, ASME J. Heat Transfer, Vol. 125, pp. 567-574.
Khanafer, K., Vafai, K., Lightstone, M., 2003 “Buoyancy-Driven Heat Transfer Enhancement in a Two-Dimensional Enclosure Utilizing Nanofluids”, Int. J. Heat Mass Transfer, Vol. 46, pp. 3639-3653.
Maiga, S. E. B., Nguyen, C. T., 2004 “Heat Transfer Behaviours of Nanofluids in a Uniformly Heated Tube”, Superlattices and Microstructures 35 , pp.543-557.
Prasher, R., 2005 “Thermal Conductivity of Nanoscale Colloidal Solutions (Nanofluids)”, Physical Review Letters, PRL 94 , pp.025901-1-025901-4.
Putra, N., Roetzel, W., Das, S. K., 2003 “Natural Convection of Nano-Fluids”, Heat and Mass Transfer, Vol. 39 , pp. 775-784.
Tseng, W., J., Wu, C., H., 2002 “Aggregation, Rheology and Electrophoretic Packing Structure of Aqueous Nanoparticle Suspensions”, Acta Materialia Vol. 50 , pp.3757-3766.
Tseng, W., J., Wu, C., H., 2003 “Sedimentation, Rheology and Particle-Packing Structure of Aqueous Suspensions”, Ceramics International Vol. 29 , pp.821-828.
Xie, H., Fujii, M., Zhang, X., 2004 “Thermal Conductivity Measurements of Nanopowder-Fluid Mixtures”, Thermal Sce]ience & Engineering, Vol. 12, No.4, pp.75-76.
Xuan, Y., Li, Q., 2000 “Heat Transfer Enhancement of Nanofluids”, Int. J. Heat and Fluid Flow, Vol. 21, pp. 58-64.
Xuan, Y., Li, Q., 2003 “Investigation on Convective Heat Transfer and Flow Features of Nanofluids”, ASME J. Heat Transfer, Vol. 125, pp. 151-155.
Xuan, Y., Li, Q., Hu, W., 2003 “Aggregation Structure and Thermal Conductivity of Nanofluids”, AIChE Journal, Vol. 49, No. 4, pp.1038-1043.
何泰安, 1999 “矩形容器內含懸浮相變化微粒之自然對流熱傳之特性實驗研究,” 國立成功大學機械工程研究所碩士論文.
林建中, 2004 “矩形容器內奈米流體之自然對流熱傳現象之研究,” 國立成功大學機械工程研究所碩士論文.