This paper deals with the experimental analysis of the influence of thermohaline natural convection on phase change liquid-solid of multicomponent mixtures. We present solidification experiments (dendritic front) from a horizontal plane heat exchanger placed in a cavity filled with a binary NH4Cl-H2O mixture. The solid grows simultaneously on the upper and lower faces of the exchanger and permits the study of two simultaneous configurations. We qualitatively study phenomena met in the presence of thermohaline convection in the liquid phase (cooling from the top) and we analyze in detail the case of the growth without convective movement in the liquid phase (cooling from the bottom). Thus, coupled effects of salt rejection and solid fraction on the front kinetics are examined by measurements of the front temperature and solid fraction. A simple model confirms the weak role played by these two phenomena for the range of characteristic parameters studied. Two conflicting effects of the solid fraction are nevertheless put in evidence.

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