On rheological characteristics of non-Newtonian nanofluids in the material forming process

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• 作者：Botong Li ; Wei Zhang ; Bin Bai ; Yanhai Lin ; Ge Kai
• 关键词：Rheological characteristics ; Nanofluid ; Power ; law fluid ; Material forming process
• 刊名：Microfluidics and Nanofluidics
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：20
• 期：11
• 全文大小：3,023 KB
• 刊物类别：Engineering
• 刊物主题：Engineering Fluid Dynamics
  Medical Microbiology
  Polymer Sciences
  Nanotechnology
  Mechanics, Fluids and Thermodynamics
  Engineering Thermodynamics and Transport Phenomena
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1613-4990
• 卷排序：20

文摘

In this paper, the material forming process (such as that of the functionally graded materials) of adding nanoparticles into non-Newtonian fluids is considered. By adding nanoparticles to a non-Newtonian fluid, a new non-Newtonian fluid is created. Thus, the rheological characteristics of the original fluid matrix have been changed. This research attempts to consider the influence of the rheological characteristics combined with the Brownian diffusion, and the thermophoresis diffusion, the distribution of nano-sized particles, the heat transfer, and the pressure drop on the process of material formation. The configuration of material treatment process is an H-height horizontal parallel plate channel with laminar forced convection nanofluids-based non-Newtonian fluids flowing through. The channel is separated by three different boundary conditions: heating, cooling, and isolated, to simulate the melting, the freezing, and the flowing processes of materials in liquid form. The non-Newtonian behaviour of nanofluids is described by the power-law model. To highlight the rheological factors of power-law nanofluids which are not the same as those of the base non-Newtonian fluids, they are assumed to vary with the quantity of the added nanoparticles in the fluid matrix, that is to say, both the consistency coefficient \(m\) and the power-law index \(n\) are considered as functions of particle loading parameter \(\phi\). Two sets of different functions of consistency coefficient \(m\) and power-law index \(n\) are used and compared in the later calculation. Method of finite element is adopted to solve the coupled momentum, energy and concentration equations, and conquer the difficulties arsing in the iteration of calculation. It is found that whether the rheological factors of non-Newtonian nanofluids are considered changeable or not would lead to very different results of the mass transfer. Also, as the parameter \(N_{\text{T}}\) (depicting the thermophoresis diffusion) increases, both temperature and concentration profiles rise, while volume fraction of particles and temperature both fall as \(N_{\text{B}}\) number (presenting the Brownian diffusion) increases. Furthermore, when two models are compared, different rheological models may possess different change rule of power-law index, but in both rheological models, the diversification of power-law index is so large that it cannot be ignored in calculation. Above all, the detailed information of velocity, temperature, and pressure drop obtained by rheological models highlights the necessity of studying the impact of rheological characteristics of non-Newtonian fluids in elaborate industrial requirements.