The aim of this paper is to summarize ten years of work in order to model the drying of solids. Nowadays there is a general agreement amongst the various researchers worldwide. If the porous medium is viewed at the so-called “macroscopic” scale (that is to say when it is viewed as a continuous and homogeneous equivalent medium) a set of three partial derivative equations is derived, three state variables being necessary to thermodynamically describe the medium (temperature, moisture content and total pressure in the gaseous phase for example).