Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Year 2006

Pietro Poesio
Università degli Studi di Brescia, Dipartimento di Ingegneria Meccanica e Industriale, Via Branze 38, 25123 Brescia, Italy

A. M. Lezzi
Università di Brescia, Italy

G. P. Beretta
Università di Brescia, Italy

Spinodal decomposition can be driven either by diffusion or convection; the importance of convection relative to diffusion is controlled by the Péclet number defined as the ratio between convective and diffusive mass fluxes. From the expression of the Péclet number, we see that diffusion is the dominating mechanism of phase segregation (i.e. the Péclet number is small) when viscosity and diffusivity are large, or when the domain characteristic size L is small. For low viscosity mixtures, convection is the dominating process so the segregation is very rapid as it takes few seconds compared to the hours in case of pure diffusion. In such cases, a strong convective flux is generated even in small sized systems and it is almost independent on the temperature difference as long as it is below the transition value. We have studied experimentally the enhancement of heat transfer in a 1 mm thick cell. We have cooled a mixture of water-acetonitrile-toulene into the two phase region so to induce convection and we have compared the efficiency of heat transfer by convection against pure conduction. We have actually noted a substantial reduction in the cooling time in case of spinodal decomposition. This study relates to the cooling or heating of small sized systems where the thermal convection can not be achieved because of the small sizes involved.

HTE-17 pages DOI: 10.1615/IHTC13.p17.170 Download article

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