Molecular Dynamics Simulation of the Effect of the Solid Gas Interface Nanolayer on Enhanced Thermal Conductivity of Copper-CO2 Nanofluid
The use of CO2 in oil recovery and in CO2 capture and storage is gaining traction in recent years. These applications involve heat transfer between CO2 and the base fluid, and hence, there arises a need to improve the thermal conductivity of CO2 to increase the process efficiency and reduce cost. One way to improve the thermal conductivity is through nanoparticle addition in the base fluid. The nanofluid model in this study consisted of copper (Cu) nanoparticles in varying concentrations with CO2 as a base fluid. No experimental data are available on thermal conductivity of CO2 based nanofluid. Molecular dynamics (MD) simulations are an increasingly adopted tool to perform preliminary assessments of nanoparticle (NP) fluid interactions. In this study, the effect of the formation of a nanolayer (or molecular layering) at the gas-solid interface on thermal conductivity is investigated using equilibrium MD simulations by varying NP diameter and keeping the volume fraction (1.413%) of nanofluid constant to check the diameter effect of NP on the nanolayer and thermal conductivity. A dense semi-solid fluid layer was seen to be formed at the NP-gas interface, and the thickness increases with increase in particle diameter, which also moves with the NP Brownian motion. Density distribution has been done to see the effect of nanolayer, and its thickness around the NP. These findings are extremely beneficial, especially to industries employed in oil recovery as increased thermal conductivity of CO2 will lead to enhanced oil recovery and thermal energy storage.
 P. Bernardo, E. Drioli, and G. Golemme, Ind. Eng. Chem. Res. 48, 4638 (2009).
 H. Yang, Z. Xu, M. Fan, R. Gupta, R. B. Slimane, A. E. Bland, and I. Wright, J. Environ. Sci. 20, 14 (2008).
 H. Masuda, A. Ebata, K. Teramae, and N. Hishinuma, Alternation of Thermal Conductivity and Viscosity of Liquid by Dispersing Ultra Fine Particles (Dispersion of Al2O3 , SiO2 and TiO2 Ultra Fine Particles), Netsu Bussei, (Japan) (1993), Vol. 7, p. 227.
 S. Lee, S. U. S. Choi, S. Li, and J. A. Eastman, ASME J. of HeatTransfer 121, 280 (1999).
 J.A.Eastman, S.U.S.Choi, S.Li, W.Yu, and L.J. Thompson, Appl. Phys. Lett. 78, 718 (2001)
 .S.U.S.Choi, Z.G.Zhang, W.Yu, F.E.Lockwood, and E.A.Grulke, Anomalous Thermal Conductivity Enhancement in Nanotube Suspensions, Appl. Phys. Lett., vol. 79, pp. 2252–2254, 2001.
 S. Jang and S. U. S. Choi, Appl. Phys. Lett. 84, 4316 (2004).
 Y. Ren, H. Xie, and A. Cai, J. Phys. D: Appl. Phys. 38, 3958 (2005).
 R. Prasher, P. Phelan, and P. Bhattacharya, Nano Lett. 6, 1529 (2006).
 S. L. Lee, R. Saidur, M. F. M. Sabri & T. K. Min. Effects of the particle size and temperature on the efficiency of nanofluids using molecular dynamic simulation, Numerical Heat Transfer, Part A: Applications Vol. 69 (2016) , Iss. 9,2016.
 J.G. Harris, K.H. Yung, J. Phys. Chem. 99 (1995) 12021.
 M. P. Allen and D. J. Tildesley, Computer Simulation of Liquids (Oxford University Press, 1989).
 Supplementary material for cutoff conditions at http://dx.doi.org/10.1063/1.4896965, structures of CO2, tabulated data of thermal conductivities, and equation of state.
 M. P. Allen and D. J. Tildesley, Computer simulation of liquids, Clarendon Press, U.K., 1987.
 S. Plimpton Lammps-Large-Scale Atomic/Molecular Massively Parallel Simulator, 2007. Available from: http:// lammps.sandia.gov/.
 W. Humphrey, A. Dalke, and K. Schulten, Vmd: Visual Molecular Dynamics, J. Mol. Graphics, vol. 14, pp. 33–38, 1996.
 T. Darden, D. York, L. Pedersen, J. Chem. Phys. 98 (1993) 10089.
 D.C.Rapaport The Art of Molecular Dynamics Simulation, Cambridge University Press, Cambridge, 2004.
 Nan Wang, Lin Shi, Jun Chen and Haifeng Jiang. Nanofluid’s Thermal Conductivity Enhancement Investigation by Equilibrium Molecular Dynamics Simulation. vol.33 (2012). IACSIT Press
 Ling Li, Yuwen Zhang, Hongbin Ma and Mo Yang. Molecular Dynamics simulation of effect of liquid layering around the nanoparticle on the enhanced thermal conductivity of nanofluids, J Nanopart Res, vol. 12 (2010), Issue 3, pp 811–821.