2. Expressions of flow

2.1 Macroscopic approach

In the previous paragraph, we described the physical phenomena at the origin of matter and heat transfer in solid foods (assimilated to porous media), generally at the pore scale. Due to the geometric complexity of pore space and the impossibility of precisely defining the domains occupied by each phase, mathematical description of transfers at this scale is, at least for the time being, not feasible. On the other hand, from the point of view of industrial process control, it is the overall effects at product scale that are important. For this reason, the transfer equations are drawn up on a macroscopic scale, which is larger than the average pore size. In this approach, the real heterogeneous medium is assimilated to a fictitious continuous medium, called...