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International Heat Transfer Conference 13
Graham de Vahl Davis (open in a new tab) School of Mechanical and Manufacturing Engineering, University of New South Wales, Kensington, NSW, Australia
Eddie Leonardi (open in a new tab) Computational Fluid Dynamics Research Laboratory, School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, Australia 2052

ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

NONEQUILIBRIUM MOLECULAR DYNAMICS STUDY ON INTERFACE HEAT AND MASS TRANSFER

page 12
DOI: 10.1615/IHTC13.p8.280
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RESUMO

We have proposed a microscopic description on the boundary condition at liquid-vapor interface using the condensation coefficient based on molecular dynamics (MD) studies and the transition state theory. The condensation coefficient, in the sense of the mean probability of condensation, is found to be an inherent property of liquid determined by the characteristic length ratio of liquid to vapor, which is the third root of free volume ratio. The condensation probability of one incident vapor particle, which is called microscopic condensation coefficient, is found to be a function of its incident translational energy and surface temperature. That is, the condensation probability is not uniform for all particles but is dependent on the kinetic energy of the incident particle individually. Also, the dependence of the microscopic condensation coefficient on the translational energy plays an important role on the kinetic boundary condition at liquid-vapor interface, particularly for the temperature profiles under nonequilibrium conditions. Present nonequilibrium molecular dynamics (NEMD) simulation with two facing surfaces of evaporating and condensing confirms that the microscopic condensation coefficient and the boundary condition for evaporation are in agreement with that for the equilibrium condition; however, the reflection shows deviation with a dependence on the nonequilibrium conditions. Also, the inverted temperature profiles between the evaporating and the condensing surfaces are found in the cases satisfying the criterions. The analyses of interfacial heat and mass fluxes show that the interfacial heat flux in the vapor phase has the negative value while the term for chemical driving force has the positive one. As a result, the interfacial entropy production rate is confirmed to be the positive value even for the cases of the inverted temperature profile based on the irreversible thermodynamics. That is, present inverted temperature profiles may occur without contradicting the second law.

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