Experimental studies of the sedimentation, stability and thermal conductivity of two different nanofluids

R. R. Souza, V. Faustino, I. Gonçalves, J. Miranda, A. Moita, A. Moreira, M. Bañobre‐López, R. Lima
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引用次数: 1

Abstract

: Fluids containing nanometer-sized particles (nanofluids, NFs) are potential candidates to improve the performance and efficiency of several thermal devices at micro- and macro-scale levels. However, the problem of sedimentation and instability of these colloidal dispersions has been the biggest obstacle for industrial-scale applications. In this work, two different NFs were tested using distilled water (DI-Water) as the base fluid. The first is a traditional NF formed by Al2O3 nanoparticles (NPs) with 50 nm diameter, and the second is a novel NF formed by poly (acrylic acid)-coated iron oxide NPs (Fe3O4@PAA) with ~10 nm diameter, obtained through a hydrothermal synthesis process. The main objective of this study was to evaluate the colloidal stability of these NFs over time using different volume fractions and compare it with DI-Water. Results involving sedimentation studies and zeta potential measurements showed that the proposed Fe3O4@PAA NF presents a higher colloidal stability compared to that of the Al2O3 NF. Additionally, thermal conductivity measurements were performed in both Fe3O4@PAA and Al2O3 NFs at different NP concentrations, using the transient plane source technique. Results showed higher thermal conductivity values for the Fe3O4@PAA NFs compared to those of Al2O3 NFs. However, a linear enhancement of thermal conductivity with increasing NPs concentration was observed for the Al2O3 NF over the whole range of NP concentrations tested, whereas two different regimes were observed for the Fe3O4@PAA NF.
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两种不同纳米流体的沉降、稳定性和导热性的实验研究
含有纳米颗粒的流体(纳米流体,NFs)是在微观和宏观水平上提高几种热器件性能和效率的潜在候选者。然而,这些胶体分散体的沉降和不稳定性问题一直是工业规模应用的最大障碍。在这项工作中,用蒸馏水(DI-Water)作为基液对两种不同的NFs进行了测试。第一种是由直径为50 nm的Al2O3纳米颗粒(NPs)形成的传统NF,第二种是由聚丙烯酸包覆直径为~10 nm的氧化铁纳米颗粒(Fe3O4@PAA)通过水热合成而成的新型NF。本研究的主要目的是使用不同的体积分数来评估这些NFs随时间的胶体稳定性,并将其与DI-Water进行比较。沉降研究和zeta电位测量结果表明,与Al2O3 NF相比,Fe3O4@PAA NF具有更高的胶体稳定性。此外,利用瞬态平面源技术,在不同NP浓度下,对Fe3O4@PAA和Al2O3 NFs的导热系数进行了测量。结果表明,Fe3O4@PAA纳米颗粒的导热系数高于Al2O3纳米颗粒。然而,在整个NP浓度测试范围内,Al2O3 NF的导热系数随NP浓度的增加呈线性增强,而Fe3O4@PAA NF的导热系数则有两种不同的情况。
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