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首页> 外文期刊>International Journal of Heat and Mass Transfer >Quantitative analyses of factors affecting thermal conductivity of nanofluids using an improved transient hot-wire method apparatus
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Quantitative analyses of factors affecting thermal conductivity of nanofluids using an improved transient hot-wire method apparatus

机译：使用改进的瞬态热线法设备定量分析影响纳米流体导热系数的因素

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摘要

While there are several factors affecting nanofluid thermal conductivity such as particle size, particle and fluid type, temperature and volume concentration, the effect of each factor on the thermal conductivity of the nanofluid is not clarified despite numerous experimental and theoretical efforts. In this work, four nanofluid samples with different particle size and volume fraction were prepared and the impact of the particle size and volume fraction on the effective thermal conductivity of the ethylene glycol/Al_2O_3 nanofluid was investigated using advanced transient hot wire system which avoids the capacitance influence and natural convection. The analysis result shows that particle size is more influential than volume fraction at the very low volume fraction less than 0.25% and the impact is more obvious with lesser volume fraction. Other than particle size and volume fraction, particle number density was turned out to be statistically very important factor affecting thermal conductivity of nanofluid when the volume fraction reaches to a certain degree of 0.2%. Under this volume fraction, the thermal conductivity of nanofluid decreases with the number density and this result may be attributed to hydrodynamic interactions induced by large fluid bodies traveling with nanoparticles in Brownian motion. This work provides not only the quantitative analyses of factors affecting the thermal conductivity of nanofluids but also the possible mechanisms of enhanced thermal conductivity.
机译：尽管有多种因素会影响纳米流体的导热性，例如粒径，颗粒和流体类型，温度和体积浓度，但是尽管进行了大量的实验和理论努力，但仍不清楚每种因素对纳米流体导热性的影响。在这项工作中，制备了四个具有不同粒径和体积分数的纳米流体样品，并使用先进的瞬态热线系统避免了电容，研究了粒径和体积分数对乙二醇/ Al_2O_3纳米流体有效导热率的影响。影响和自然对流。分析结果表明，在小于0.25％的极低体积分数下，粒径比体积分数更具影响力，而体积分数越小，其影响越明显。除了粒径和体积分数之外，当体积分数达到一定程度的0.2％时，事实证明，颗粒数密度是影响纳米流体的热导率的非常重要的因素。在此体积分数下，纳米流体的热导率随数密度的增加而降低，并且该结果可能归因于大型流体与纳米粒子在布朗运动中运动引起的流体动力相互作用。这项工作不仅提供了影响纳米流体导热系数的定量分析，而且还提供了提高导热系数的可能机制。

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