Simulation of grape stalk deep-bed drying

A mathematical representation of grape stalk deep-bed drying with variable air conditions over time and bed positions was developed. The model considers the heat and mass transfer (conduction and diffusion) within the different structures of the grape stalk: three infinite cylinders and one spherical, and the heat and mass balances in the bulk air. The bed was represented assuming ideal mixed stages. A simulator was obtained from the model solution, and validated with experimental drying curves of grape stalk obtained in a plant pilot drier. The simulator adequately predicts the experimental behaviour for grape stalk average moisture and the air output temperature during drying.