General modeling considerations
Heat transfer in porous media - Phase Change

In view of its particular practical importance, the following section deals only with the case of liquid-vapor phase change (evaporation-condensation). The comparatively less studied liquid-solid phase change (although it is involved in many applications: snow melting, metallurgy/foundrying, etc.) is not addressed. Let us simply point out that solidification of a multiconstituent mixture involves two mechanisms, dominated by possible instabilities at the fluid/solid interface:

• columnar growth from the cooling surface, leading to the presence of a porous medium ("mushy zone");

• growth of equiaxed grains in the cooling liquid solution.

Porous media" models have therefore been developed.