Mathematical modeling of impingement drying of corn tortillas

Impingement drying of corn tortillas was modeled using governing equations for heat and mass transfer during the drying process. Mass transfer within the product was modeled as diffusion-driven mass flux. Heat transfer was dr iven according to Fourier's Law of conduction. Boundary conditions for dryi ng in both air and superheated steam were incorporated into the model. Conv ective heat transfer accounted for heat flow into the product at the surfac e. When drying in air, convective mass transfer prevailed; in superheated s team, differences in vapor pressure between the drying medium and the produ ct surface accounted for mass transfer. Temperature and moisture content pr edictions followed the experimental trends with both air and steam drying ( 115-145 degreesC). Steam condensation unaccounted for by the model resulted in underpredictions in the moisture content in steam drying at low tempera tures. Product thickness and drying medium temperature had a significant ef fect on moisture content and temperature profile over time. (C) 2001 Elsevi er Science Ltd. All rights reserved.