本文係以實驗量測與數值模擬方式探討矩形容器內奈米流體之自然對流熱傳現象。所探討之理論模型為一左邊加熱及右邊冷卻的矩形容器，而其餘邊界皆為絕熱壁。理論模式關係式中，將奈米流體之熱傳導係數隨溫度及濃度變化效應以及奈米粒子間的相對速度效應列入考慮，而數值模擬主要考慮參數範圍為：萊利數(Ra=1.E+04 ~1.E+07 )；普蘭特數(Pr=6.5)；奈米粒子質量濃度(Cm=3.52%、6.86%、10.04% )、奈米粒子無因次粒徑(Dp=2.55.E-06 )及有效粒徑修正倍數( Rc=1、10、100)。就數值模擬結果顯示，在上述萊利數範圍下，其奈米流體熱傳率皆較純水為佳，並且隨濃度之增加而提升。實驗之物理模形，考慮五組不同之奈米流體質量濃度，及其相對應之不同萊利數變化，就實驗結果和數值模擬相互比較發現，奈米流體熱傳率會有明顯的降低，而矩形容器內之熱傳現象，取決於萊利數及濃度。

　　The problem of two-dimensional steady state natural convection heat transfer in a square enclosure filled with nanofluids has been investigated numerically and experimentally. The enclosure is differentially heated across two vertical walls of the enclosure while the remaining side walls are assumed adiabatic. In the numerical formulation, the effects of variable thermal conductivity of the nanofluids associated with temperature and particle fraction as well as of the settling velocity of the nanoparticles with respect to the bulk fluid have been accounted. The numerical simulations have been undertaken for the pertinent dimensionless parameters in the following ranges: the Rayleigh number,Ra=1.E+04 ~1.E+07 ; the Prandtl number,Pr =6.5; the mass fraction of the nanoparticles,Cm= 3.52%, 6.86%, 10.04%; the dimensionless particle diameter,Dp=2.55.E-06 ; the effective particle clustering factor, Rc=1,10,100. Numerical results clearly indicate that in comparison with the heat transfer results of the pure fluid for the range of Rayleigh number considered, incorporating the nanofluids of various mass fractions can always result in significant heat transfer enhancement. On the other hand, experiments mimicking the physical configuration considered have been conducted mainly for five different mass fractions under various Rayleigh numbers. Contrary to the numerical findings, the experimental measurements reveal that using the nanofluids may result in marked reduction, instead of enhancement, of the transfer across the enclosure, depending on the Rayleigh number and the mass fraction.

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