Effect of aggregation state on the thermal conductivity of nanofluids

被引：0

作者：

Chen W. ^{[1
]}

Wang S. ^{[1
]}

Zhai Y. ^{[1
]}

Li Z. ^{[1
]}

机构：

[1] State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Yunnan, Kunming

来源：

Huagong Jinzhan/Chemical Industry and Engineering Progress | 2023年 / 42卷 / 11期

关键词：

aggregation structure; interfacial layer; molecular dynamics; nanofluids; thermal conductivity;

D O I：

10.16085/j.issn.1000-6613.2022-2257

中图分类号：

学科分类号：

摘要：

Nanofluids consist of basefluids and nanoparticles, which have attracted wide attention because of their favorable thermal properties. The thermal conductivity of nanofluids is greatly affected by particles aggregation which is one of the significant characteristics of nanofluids. Currently, it is difficult to observe the microscopic changes in nanofluids from uniform dispersion to agglomeration by experimental method. The non-equilibrium molecular dynamics (NEMD) method was performed to investigate the Brownian motion of basefluid atoms and interfacial layer properties during particle agglomeration of Cu/Ar nanofluid. The mechanism of the effect of agglomeration behavior on the variation of thermal conductivity was obtained by analyzing microscopic parameters such as mean square displacement (MSD) and number density. The results showed that the thermal conductivity of nanofluid gradually increased during the process of nanoparticles from uniform dispersion to complete agglomeration, and the thermal conductivity obtaind the maximum value when the particles were agglomerated. Comparing the MSDs in the two states of uniform dispersion and complete aggregation of the particles, the MSD value of the base fluid atoms of fully agglomerated state increased by about 3% compared to that of uniformly dispersed state, showing that the Brownian motion of the base fluid atoms of fully agglomerated state was enhanced. Meanwhile, the MSD of the interfacial layer of fully agglomerated state decreased by about 22% compared to that of uniformly dispersed state, indicating that the atoms in the interfacial layer were less active and the interfacial layer tended to be stable. Furthermore, the aggregation structure of the particles was investigated. The agglomerated structures can be classified into reaction-limited agglomerates (21Å,1Å=0.1nm) and diffusion-limited agglomerates (22Å) by varying the initial particle center-of-mass distance. After increasing the number density of the nanofluidic interfacial layer from the initial value of 67nm-3 to 72nm-3, the reaction-limited agglomeration shifted to diffusion-limited aggregation. After decreasing the number density of the nanofluidic interfacial layer from the initial value of 67nm-3 to 62nm-3, the diffusion-limited aggregation shifted to reaction-limited aggregation. The results showed that the density of interfacial layer was one of the main factors affecting the aggregation structure of nanoparticles. © 2023 Chemical Industry Press. All rights reserved.

引用

页码：5700 / 5706

页数：6

共 21 条

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