Nanofluids are suspensions of nanoparticles in a base heat-transfer liquid. They have been widely investigated to boost heat transfer since they were proposed in the 1990s. We present a statistical correlation analysis of experimentally measured thermal conductivity of water-based nanofluids available in the literature. The influences of particle concentration, particle size, temperature and surfactants are investigated. For specific particle materials (alumina, titania, copper oxide, copper, silica and silicon carbide), separate analyses are performed. The conductivity increases with the concentration in qualitative agreement with Maxwell’s theory of homogeneous media. The conductivity also increases with the temperature (in addition to the improvement due to the increased conductivity of water). Surprisingly, only silica nanofluids exhibit a statistically significant effect of the particle size, whereby smaller particles lead to faster heat transfer. Overall, the large scatter in the experimental data prevents a compelling, unambiguous assessment of these effects. Taken together, the results of our analysis suggest that more comprehensive experimental characterizations of nanofluids are necessary to estimate their practical potential.

纳米流体是纳米颗粒在基础传热液体中的悬浮液。自 1990 年代提出以来，它们已被广泛研究以促进传热。我们对文献中可用的水基纳米流体的实验测量热导率进行了统计相关分析。研究了颗粒浓度、粒径、温度和表面活性剂的影响。对于特定的颗粒材料（氧化铝、二氧化钛、氧化铜、铜、二氧化硅和碳化硅），分别进行分析。电导率随着浓度的增加而增加，与麦克斯韦的均质介质理论定性一致。电导率也随温度增加（除了由于水的电导率增加而提高）。出奇，只有二​​氧化硅纳米流体表现出对粒径的统计显着影响，因此较小的颗粒会导致更快的热传递。总体而言，实验数据的大量分散阻碍了对这些影响的令人信服的、明确的评估。综上所述，我们的分析结果表明，需要对纳米流体进行更全面的实验表征以估计其实际潜力。