Resistances for heat and mass transfer through a liquid-vapor interface in a binary mixture

In this paper we calculate the interfacial resistances to heat and mass transfer through a liquid-vapor interface in a binary mixture. We use two methods, the direct calculation from the actual non-equilibrium solution and integral relations, derived earlier. We verify, that integral relations, being a relatively faster and cheaper method, indeed gives the same results as the direct processing of a non-equilibrium solution. Furthermore we compare the absolute values of the interfacial resistances with the ones obtained from kinetic theory. Matching the diagonal resistances for the binary mixture we find that kinetic theory underestimates the cross coefficients. The heat of transfer is as a consequence correspondingly larger.Comment: 15 pages, 5 figure

Nonequilibrium translational effects in evaporation and condensation

This paper shows how mesoscopic nonequilibrium thermodynamics can be applied to condensation and evaporation. By extending the normal set of thermodynamic variables with two internal variables, we are able to give a new theoretical foundation for a mechanism of condensation that has been proposed from molecular simulation results. The flux does not follow a simple Arrhenius formula for small activation energies which are relevant here.Comment: To appear in J. Chem. Phy

Non-equilibrium Thermodynamics for Quantum Systems

The extension of the scheme of mesoscopic non-equilibrium thermodynamics developed for quantum mechanical systems by Bedeaum and Mazur (2001) is discussed. This scheme gives a master equation for the density matrix of the system. Onsager relations are given. Application to a spin system gives the Bloch equations. The application to a one-dimensional harmonic oscillator results in equations which make it possible to calculate the Green functions. For the last case we derive, as a new alternative, quantum mechanical Langevin equations. Compared to the classical Langevin equations a new element is random velocity. The correlation of the random velocity with the random force then results from the zero point motion of the oscillator. The application of mesoscopic non-equilibrium thermodynamics to these well known problems illustrates the usefullness of this method

Transport of heat and mass in a two-phase mixture. From a continuous to a discontinuous description

We present a theory which describes the transport properties of the interfacial region with respect to heat and mass transfer. Postulating the local Gibbs relation for a continuous description inside the interfacial region, we derive the description of the Gibbs surface in terms of excess densities and fluxes along the surface. We introduce overall interfacial resistances and conductances as the coefficients in the force-flux relations for the Gibbs surface. We derive relations between the local resistivities for the continuous description inside the interfacial region and the overall resistances of the surface for transport between the two phases for a mixture. It is shown that interfacial resistances depend among other things on the enthalpy profile across the interface. Since this variation is substantial the coupling between heat and mass flow across the surface are also substantial. In particular, the surface puts up much more resistance to the heat and mass transfer then the homogeneous phases over a distance comparable to the thickness of the surface. This is the case not only for the pure heat conduction and diffusion but also for the cross effects like thermal diffusion. For the excess fluxes along the surface and the corresponding thermodynamic forces we derive expressions for excess conductances as integrals over the local conductivities along the surface. We also show that the curvature of the surface affects only the overall resistances for transport across the surface and not the excess conductivities along the surface.Comment: 25 pages, 2 figure