Estimation of Thermal Conductivity of Nanofluids Using MD-Stochastic Simulation Based Approach

Authors: Sujoy Das, M. M. Ghosh

Abstract:

The thermal conductivity of a fluid can be significantly enhanced by dispersing nano-sized particles in it, and the resultant fluid is termed as "nanofluid". A theoretical model for estimating the thermal conductivity of a nanofluid has been proposed here. It is based on the mechanism that evenly dispersed nanoparticles within a nanofluid undergo Brownian motion in course of which the nanoparticles repeatedly collide with the heat source. During each collision a rapid heat transfer occurs owing to the solidsolid contact. Molecular dynamics (MD) simulation of the collision of nanoparticles with the heat source has shown that there is a pulselike pick up of heat by the nanoparticles within 20-100 ps, the extent of which depends not only on thermal conductivity of the nanoparticles, but also on the elastic and other physical properties of the nanoparticle. After the collision the nanoparticles undergo Brownian motion in the base fluid and release the excess heat to the surrounding base fluid within 2-10 ms. The Brownian motion and associated temperature variation of the nanoparticles have been modeled by stochastic analysis. Repeated occurrence of these events by the suspended nanoparticles significantly contributes to the characteristic thermal conductivity of the nanofluids, which has been estimated by the present model for a ethylene glycol based nanofluid containing Cu-nanoparticles of size ranging from 8 to 20 nm, with Gaussian size distribution. The prediction of the present model has shown a reasonable agreement with the experimental data available in literature.

Keywords: Brownian dynamics, Molecular dynamics, Nanofluid, Thermal conductivity.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1338058

References:

[1] Eastman J. A., Choi S. U. S., Li S., Yu W., and Thompson L. J., "Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles", Applied Physics Letters, 78, pp. 718-720, 2001.
[2] Choi S. U. S., Zhang Z. G., Yu W., Lockwood F. E., and Grulke E. A., "Anomalous thermal conductivity enhancement in nanotube suspensions", Applied Physics Letters, 79, pp. 2252-2254, 2001.
[3] Das S. K., Putra N., Thiesen P., and Roetzel W., "Temperature Dependence of Thermal Conductivity Enhancement for Nanofluids", Journal of Heat Transfer, 125, pp. 567-574, 2003.
[4] Patel H. E., Das S. K., Sundararajan T., Nair A. S., George B., and Pradeep T., "Thermal conductivities of naked and monolayer protected metal nanoparticle based nanofluids: Manifestation of anomalous enhancement and chemical effects", Applied Physics Letters, 83, pp. 2931-2933, 2003.
[5] Lee S., Choi S. U. S., Li S., and Eastman J. A., "Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles", Journal of Heat Transfer, 121, pp. 280-289, 1999.
[6] Shukla R. K. and Dhir V. K., "Study of the effective thermal conductivity of nanofluids", in: Proceedings of the ASME International Mechanical Engineering Congress and Exposition (Orlando, Florida, USA), November 5-11, 2005, pp. 1-5.
[7] Bhattacharya P., Saha S. K., Yadav A., Phelan P. E., and Prasher R. S., "Brownian dynamics simulation to determine the effective thermal conductivity of nanofluids", Journal of Applied Physics, 95, pp. 6492- 6494, 2004.
[8] Jang S. P. and Choi S. U. S., "Role of Brownian motion in the enhanced thermal conductivity of nanofluids", Applied Physics Letters, 84, pp. 4316-4318, 2004.
[9] Prasher R., Bhattacharya P., and Phelan P. E., "Brownian-Motion-Based Convective-Conductive Model for the Effective Thermal Conductivity of Nanofluids", Journal of Heat Transfer, 128, pp. 588-595, 2006.
[10] Leong K. C., Yang C., and Murshed S. M. S., "A model for the thermal conductivity of nanofluids-the effect of interfacial layer", Journal of Nanoparticle Research, 8, pp. 245-254, 2006.
[11] Prasher R., Evans W., Meakin P., Fish J., Phelan P., and Keblinski P., "Effect of aggregation on thermal conduction in colloidal nanofluids", Applied Physics Letters, 89, p. 143119, 2006.
[12] Maxwell J. C., A Treatise on Electricity and Magnetism, 2nd ed., Oxford University Press, Cambridge, 1904, pp. 435-441.
[13] Hamilton R. L. and Crosser O. K., "Thermal Conductivity of Heterogeneous Two-Component Systems", I & EC Fundamentals, 1, pp. 187-191, 1962.
[14] Bonny G., Pasianot R. C., Malerba L., and Castin N., "Ternary Fe-Cu-Ni many-body potential to model reactor pressure vessel steels: First validation by simulated thermal annealing", Phylosophical Magazine, 89, pp. 3531-3546, 2009.
[15] Nelson E., Dynamical Theories of Brownian Motion, 2nd ed., (Princeton University Press, New Jersey, USA, 2001), Ch. 9, pp. 45-52.
[16] John W., Reischl G., and Devor W., "Charge transfer to metal surfaces from bouncing aerosol particles", Journal of Aerosol Science, 11, pp. 115-138, 1980.
[17] Bandyopadhyay K., Ghosh K. S., and Ghosh M. M., "Molecular dynamics based approach for the estimation of tensile properties of nanoparticles" (unpublished).
[18] Garg J., Poudel B., Chiesa M., Gordon J. B., Ma J. J., Wang J. B., Ren Z. F., Kang Y. T., Ohtani H., Nanda J., McKinley G. H., and Chen G., "Enhanced thermal conductivity and viscosity of copper nanoparticles in ethylene glycol nanofluid", Journal of Applied Physics, 103, p. 074301, 2008.