A General model for wax diffusion in crude oils under thermal gradient

We consider a general model for the complex phenomenon of wax deposition in crude oils. Wax is present either as dissolved in oil or suspended as a crystallized phase. The solubility of wax decreases very sharply with temperature. The presence of a thermal gradient induces both a dynamics of transfer from dissolved to solid phase and the formation of a gel--like deposit layer at the cold wall. The process is described including different stages of evolution: we start from the fully saturated system, then, after the onset of an unsaturated front we deal with the simultaneous presence of saturated and unsaturated regions up to the complete unsaturation of the system.