ABSTRACT
In food processing, simultaneous heat and mass transfer operations and, sometimes, chemical reactions are involved. Understanding the key physics involved in the simultaneous heat and mass transfer processes in foods is highly challenging. Constructing an ideal isothermal drying device without volumetric heating such as microwave or radio frequency heating, may not be possible unless the mass transfer resistance is not high inside the porous material being dried. Mass transfer from the sharp moving front and the vapor exit surface is often modeled using a simple effective diffusion concept. This mass transfer is regarded sometimes as the rate limiting process form air-drying the mass-transfer limiting process. In this case, the vapor concentration at the evaporation front is taken to be the highest. Since the nonlinear nature of the models described above, in particular, when the models are highly coupled between heat and mass transfer, instability and sometimes numerical diffusion can be introduced.
