High pressure technology opens new possibilities for freezing and thawing of liquid and solid substances. In the present contribution modelling and numerical simulation of high pressure induced freezing and thawing processes of a fluid food system is presented. Phase transitions between water and ice I under pressure in the range 0.1 – 200 MPa are simulated accounting for convective motion of the liquid phase. The results of the simulation are presented and temperature, velocity as well as liquid and solid phase distributions are studied. It is shown that the spatial propagation of the ice front depends very strong on the temperature and velocity field.