颗粒尺寸对纳米流体自然对流模式影响的格子Boltzmann方法模拟  

Lattice Boltzmann method simulated effect of nanoparticle size on natural convection patterns of nanofluids

作　　者：隋鹏翔 Sui Peng-Xiang(College of Elementary Education,Capital Normal University,Beijing 100048,China)

机构地区：[1]首都师范大学初等教育学院,北京100048

出　　处：《物理学报》2024年第23期144-156,共13页Acta Physica Sinica

基　　金：北京市教育委员会科技计划一般项目(批准号:KM202410028009)资助的课题.

摘　　要：采用无量纲格子玻尔兹曼(non-dimensional lattice Boltzmann method,NDLBM)对方腔内纳米流体的自然对流进行数值模拟,讨论克努森数(10^(-6)≤Knf,s≤10^(4))、瑞利数(10^(3)≤Raf,L≤10^(6))、颗粒体积分数(10^(-2)≤φs≤10^(-1))等参数对纳米流体流动和传热的影响.结果表明:在不同Raf,L下,颗粒粒径对传热效率的影响是不同的.在低Raf,L的热传导区间,颗粒粒径对传热影响较小;在高Raf,L的热对流区间,较大的颗粒粒径显著提升了流动强度和传热效率.若保持Raf,L和φs不变,随着颗粒粒径的减小,纳米流体的传热方式由热传导转变为热对流.此外,针对高Raf,L的热对流区间,在兼顾了导热和流动性的情况下,最大传热效率所对应的颗粒体积分数为φs=8%.最后,通过分析平均努塞尔数■和纳米流体相较于基液增加传热率Ren,f随不同无量纲参数变化的三维等值面图,发现■和Ren,f的极值均出现在颗粒粒径为Knf,s=10^(-1).基于数值结果,构建■与Knf,s,Raf,L,φs之间的函数关系式,揭示了这些无量纲参数对传热性能的影响.In this work,numerical simulation of natural convection of nanofluids within a square enclosure are conducted by using the non-dimensional lattice Boltzmann method(NDLBM).The effects of key governing parameters Knudsen number(10^(-6)≤Knf,s≤10^(4)),Rayleigh number(10^(3)≤Raf,L≤10^(6)),and nanoparticle volume fraction(10^(-2)≤φs≤10^(-1))on the heat and mass transfer of nanofluids are discussed.The results show that in the low Raf,L conduction dominated regime,the nanoparticle size has little effect on heat transfer,whereas in the high Raf,L convection dominated regime,larger nanoparticle size significantly enhances flow intensity and heat transfer efficiency.For fixed Raf,L andϕs,the heat transfer patterns change from conduction to convection dominated regime with Knf,s increasing.The influence of nanoparticle volume fraction is also investigated,and in the convection-dominated regime,the maximum heat transfer efficiency is achieved whenϕs=8%,balancing thermal conduction and drag fore of nanofluid.Additionally,by analyzing the full maps of mean Nusselt number(■)and the enhancement ratio related to the base fluid(Ren,f),the maximum value of ■ and Ren,f occur when the nanoparticle size is Knf,s=10^(−1) for both conductive and convection dominated regime.To ascertain the effects of all key governing parameters on ■,a new empirical correlation is derived from the numerical results,providing a more in-depth insight into how these parameters influence on heat transfer performance.

关 键 词：克努森数 纳米流体 自然对流 格子玻尔兹曼方法 

分 类 号：O35[理学—流体力学]