A generalized conjugate model for forced convection drying based on an evaporative kinetics

A model describing the heat and mass transfer involved in food drying is presented. The aim is to determine the effect of air temperature on the performance of the drying process applied to fresh-cut vegetable slices, but other effects can be easily incorporated in the model. The model allows to disregard one of the most limiting parameters in such modeling, i.e. the average heat and mass transfer coefficients at the food/drying substrate interface, which are generally taken from the literature. Such assumptions are limiting in the sense that they are referred to average transfer conditions and general geometries. The presented model relies upon a finite-element solution of time-dependent differential equations for simultaneous and conjugate heat and moisture transfer in a two-dimensional domain, without any inference in such empiricism. A special formulation for drying kinetic of the substrate is also exploited, and a treatment of the dependence of the properties upon the residual moisture content is included. After proper validation with the available experimental measurements, the numerical solution is discussed by presenting each involved field variables, emphasizing on the conjugate nature of the drying process. Due to its flexibility and generality, the model can be used in common industrial driers’ optimization, even in the assumption of a laminar flow field.