In this study, with reference to the drying process of carrot
slice, water and heat transfers were modelled by transient
mass and energy balances, respectively, whereas
evaporation at air–food interface was considered by defining
proper boundary conditions expressed in terms of heat
and mass transfer coefficients estimated by the well-known
empirical correlations (Perry & Green, 1984).
The model is based on the following hypotheses:
• Heat transfer in the product was by conduction;
• Mass transfer in the product was by diffusion;
• Transport of water vapour within dehydrated material
was negligible;
• No food shrinkage occurred during drying;
• A bidimensional rectangular domain (0.6 cm long with a
thickness ranging from 0.3 to 1.5 cm) was considered;
• The drying air was supplied continuously to the product,
and its flow was parallel to its major surfaces;
• Heat and mass transfer resistance were negligible across
the net on which food was placed (Thorvaldsson &
Janestad, 1999; Viollaz & Rovedo, 2002).