A cross-regional thermo-hydro transport model for vacuum pre-cooling

Vacuum pre-cooling of food products after harvesting is a multiphysics problem coupling the fluid flow, heat and mass transfer, on which a series of numerical simulations have been performed. However, Multiphase flow with cross-regional nature is not coupled with heat and mass transfer processes, which is inconsistent with the actual vacuum pre-cooling process and makes the simulation results inaccurate. Taking shiitake mushroom (Lentinula edodes) as an example, a multiphase porous media model modified by the cross-regional phase transition equation for the thermo-hydro coupling of food vacuum pre-cooling (MTH) was established in this paper. The accuracy of the proposed model is validated by experimental results. The results show that the average errors corresponding to pressure, temperature, and weight loss were 23.47%, 6.29%, and 17.6% respectively. Compared with the traditional thermo-hydro coupling model (TH), the MTH model is more sensitive to pressure change, the average errors of temperature and weight loss are reduced by 4.19%, 9.89% respectively. Both models result in the lowest weight loss when the humidification ratio is close to 2%. In further, the simulation results predict the development of the evaporation front from the edge of the evaporation zone towards the inner core. The model developed in this paper considering cross-regional phase transition contributes to an in-depth understanding of the mechanism of vacuum cooling.