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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

ACOUSTIC HEATING AND BUOYANCY-DRIVEN INSTABILITY INDUCED BY MASS TRANSPORT IN A NEAR-CRITICAL BINARY FLUID MIXTURE

Get access (open in a dialog) DOI: 10.1615/IHTC16.cov.022654
pages 3277-3294

Résumé

Approaching the liquid-vapor critical point, strong anomalies in thermodynamic and transport properties induce a fast heat transfer mechanism called the piston effect. In this study, we identify a piston-effect-like phenomenon and the ensuing buoyancy-driven instability in a Rayleigh-Bnard-like problem: a near-critical dilute binary fluid mixture confined in a rectangular cavity submitted to concentration increase at the bottom in the presence of gravity. The results were obtained by numerical simulations. They show that after the concentration increase, a thin diffusive layer with both concentration and temperature gradients forms and expands due to the diverging expansion coefficients and the vanishing diffusivities, causing a homogeneous acoustic heating in bulk fluid. The progressively growing boundary layer leads to the onset of convection, which improves the mass transfer in the whole domain than a purely diffusive way. The evolution of velocity field in a long time is described, with an emphasis on the abnormal velocity fluctuations caused by the strong coupling between concentration and density during the early stage of convection.