Heat and mass transport in nanoconfined colloidal fluids

Miller, N 2013, Heat and mass transport in nanoconfined colloidal fluids, Doctor of Philosophy (PhD), Applied Science, RMIT University.

Document type: Thesis
Collection: Theses

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Title Heat and mass transport in nanoconfined colloidal fluids
Author(s) Miller, N
Year 2013
Abstract In this study we have investigated the effects of thermophoresis in two component mixtures. Thermophoresis is the movement of molecules caused by a temperature gradient. To understand how colloidal fluids behave on the nanoscale, we have investigated heat and mass transport of bulk homogeneous fluids, and the effects of heat and mass transport in highly confined systems. This has facilitated our understanding of the separation of colloidal fluids and their behaviour when subject to a temperature difference, or experiencing planar Poiseuille flow. Understanding and characterising the separation behaviour of colloidal fluids is important to a number of fields of science and engineering, including lab-on-a-chip technology. To confirm the method presented in this work for obtaining transport coefficients of binary mixtures, we have used equilibrium molecular dynamics to obtain the transport coefficients for an equimolar argon-krypton fluid, and confirmed our results with those in the literature.

The method is then used to obtain the transport coefficients for a slightly more realistic hard core colloidal fluid over a range of concentrations and temperatures. For both the equimolar argon-krypton and the colloid, we show how these coefficients can be used to obtain a continuum description of the velocity, temperature and concentration profiles across a confining channel. We show how the values of the transport coefficients obtained from the bulk can be used to predict the separation of two component fluids. Two situations are reported, firstly a temperature gradient system with no flow. The temperature gradient is imparted on the fluid by maintaining different temperatures at the confining walls. The second system is planar Poiseuille flow, where the temperatures of the walls are equal, and a gravitational like field is applied equally to all species of the fluid. Having successfully shown that for both equimolar argon-krypton and the colloid, the separation of the colloid can be predicted. We then show the limitations of the theory presented in this work, when the colloidal fluid is subject to higher field strengths, and subsequent increased flow rates. By completing this work we have successfully contributed knowledge about the role that diffusive and heat fluxes play in the field of colloidal science and nanotechnology. We provide a framework for the correct evaluation of transport coefficients of binary solutions, and show how to predict colloid separation for confined systems.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Applied Science
Keyword(s) Nanofluidics
Molecular Dynamics
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Created: Fri, 01 Nov 2013, 09:15:20 EST by Denise Paciocco
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