Effects of concentration and temperature on the coupled heat and mass transport in liquid mixtures

Using published experimental data on the thermal conductivity, mutual diffu sivity, and heats of transport, the degree of coupling between heat and mas s flows has been calculated for binary and ternary nonideal liquid mixtures . The binary mixtures consist of two types: the first is six systems of six -to-eight-carbon straight and branched chain alkanes in chloroform and in c arbon tetrachloride; and the second is mixtures of carbon tetrachloride wit h benzene, toluene, 2-propanone, n-hexane, and n-octane. The ternary mixtur e considered is toluene-chlorobenzene-bromobenzene. The published data are available at 25 degreesC, 30 degreesC and 35 degreesC and ambient pressure. Using the linear nonequilibrium thermodynamics (LNET) and the dissipation- phenomenological equation (DPE) approach, the effects of concentration, tem perature, molecular weight, chain-length, solute, solvent, and branching on the degree of coupling are examined. The extent of coupling and the therma l diffusion ratio are expressed in terms of the transport coefficients to o btain a better understanding of the interactions between heat and mass flow s in liquid mixtures. It is found that the composition of the heavy compone nt bromobenzene changes the direction and magnitude of the two-Flow couplin g in the ternary mixture. (C) 2001 Elsevier Science Ltd. All rights reserve d.