Speeding up of heterogeneous reactions in near-critical phases

In the last decade, it has been shown that an interface reaction taking place in a gaseous mother-phase could be affected by the existence of thermo-acoustic convection in the fluid, due to its compressibility. In particular, crystal growers involved in space experiments have been concerned by such kinds of problems, as the absence of gravitational convection can make thermo-acoustic convection predominent above other transport phenomena. It was consequently natural to investigate the effect of compressibility on interface reactions taking place in supercritical mother phases, which are known to exhibit a diverging compressibility. In the present study, matched asymptotic expansions methods are applied to the 1-D Navier-Stokes equations written for a near-critical van der Waals gas, in order to investigate the response of an interface reaction to a thermal disturbance. It is shown that the high compressibility of the fluid may provoke in some cases a strong increase of the flux of matter at the interface. A mechanism is put in evidence, which could, among others, contribute to the strong corrosion effects witnessed in supercritical fluid containers.