Numerical simulation of heat and mass transfers in a supercritical mixture submitted to a heterogeneous reaction.

Near the liquid-gas critical point, fluid properties are intermediate between those of liquids and gases and they strongly depend on temperature and pressure. These tunable properties allowed the development of many processes where supercritical fluids are used instead of conventional organic solvents: extraction and purification, particle production, material processing… In spite of the use of supercritical fluids in several industrial applications, the consequences of the specific transport properties near the liquid-gas critical point are not totally elucidated. For example, we know that the divergence of transport coefficients as the critical point is approached induces peculiar phenomena, such as a fast thermal relaxation by a thermoacoustic effect. For mixtures where the majority component is close to its critical point, the behavior of a heterogeneous reaction (such as adsorption-desorption, crystal growth, dissolution) is likely to be also influenced. A preliminary study was performed for a strongly dilute binary mixture with a simplified model for the reaction at the solid boundaries (Raspo, Meradji, Zappoli, Chemical Engineering Science, 62, pp. 4182-4192, 2007). This one-dimensional study showed that, in a special zone of the mixture phase diagram, peculiar behaviors can actually be observed.

The aim of the contract is to continue this preliminary work by accounting for two-dimensional situations and a more realistic heterogeneous reaction. Simulations will be performed using an in-house two-dimensional computational code based on spectral methods. This code solves the Navier-Stokes equations coupled with energy and species diffusion equations and the Peng-Robinson equation of state to model the supercritical fluid. It will be necessary to choose first a model binary mixture, and then to modify the code to take into account a more realistic model for the reaction at the boundaries, and potentially non-dilute mixtures.

The candidate must have a thesis and at least two years’ experience. He (she) must have also reliable knowledge in fluid mechanics and a previous experience in numerical simulation of reactive fluid flows. A preliminary experience with spectral approximations would be appreciated. A perfect mastery of French is required.

Workplace: Laboratoire M2P2, UMR7340 CNRS-AMU-Ecole Centrale de Marseille, France.

Duration: 12 months.

Beginning: 2015 (as soon as possible).

Contact Person: Isabelle RASPO, isabelle.raspo<στο>univ-mrs.fr