Multiphase porous media model with thermo-hydro and mechanical bidirectional coupling for food convective drying

摘要

Food convective drying is a multiphysics problem coupling the fluid flow, heat transfer, mass transfer and shrinkage, on which a series of numerical simulation has been performed. However, the material shrinkage is not coupled properly with the heat and mass transfer process, which is inconsistent with actual drying process and makes the simulation results inaccurate. Furthermore, the effect of shrinkage on heat and mass transfer during the food convective drying process hasn't been fully studied. Taking shiitake mushroom (Lentinula edodes) as an example, a multiphase porous media model with thermo-hydro and mechanical bidirectional coupling (THM) for food convective drying is established in this paper. The accuracy of proposed model is validated by experiment results. Base on the proposed model, the shrinkage process of the shiitake mushroom during drying is analyzed in detail, and the effect of shrinkage on heat and mass transfer is studied by comparing with the thermo-hydro coupling model (TH). Compared with the traditional TH model, the proposed THM model presents a faster decrease of moisture content, which consists better with the experiment results. Also, there is larger evaporation rate with a relative deviation of 29.5% at the peak. Besides, lagging movement of the high evaporation rate area towards the internal region of shiitake mushroom is observed. What's more, the temperature of shiitake mushroom from THM model is lower than that from TH model with the maximum temperature difference of 3°C, and the temperature in the internal region of shiitake mushroom presents a slower rise. The model established in this paper that considers the shrinkage can accurately simulate the food convective drying process and help to deeply understand the mechanism of convective drying. In engineering practice, the proposed model can provide technical support for optimizing the drying process and improving the product quality.