The drying process is largely used in many different industrial applications, such as treatment of foods, production of cosmetics and pharmaceuticals, manufacturing of paper, wood and building materials, polymers and so on. Physical and mathematical models can constitute useful tools to establish the influence of the main process variables on the final product quality, in order to apply an effective production control. In this work, simulation model was developed to describe combined convective/microwave assisted drying. In particular, a multi-physics approach was applied to take into account heat and two mass balances (for liquid water and for water vapor) and Maxwell's equations to describe electromagnetic field propagation. Potato matrix was selected as food material; a waveguide with a rectangular cross section, equipped with a hot air circulator device, was used as microwave applicator. The proposed model was found able to describe the process, being thus a useful tool for design and management of the process itself.