MODELAGEM MATEMÁTICA E PROPRIEDADES TERMODINÂMICAS DA SECAGEM DO GRÃO DE GIRASSOL.

It was intended, in the present work, to adjust mathematical models to the drying kinetics of the sunflower grains (Helianthus annuus) in various temperature conditions, as well as to determine the effective liquid diffusion and the thermodynamic properties. Sunflower beans were used manually harvested in the municipality of Santa Helena de Goiás - Goiás, with the initial moisture content of 0,348 ± 0,014 dry base (decimal, B.S.). The grains were subjected to kiln drying with forced air ventilation at temperatures of 40, 60, 80 and 100 °C. It is concluded that all models analyzed are able to represent the drying of the sunflower grain, however the model of Page was chosen as best due to its greater simplicity when compared to the other models analyzed. The increase in the drying temperature promotes greater diffusivity of water in the seeds, and the activation energy for the process is 26.28 kJ mol-1. In the drying of sunflower grains, the enthalpy falls drastically with the increase in temperature. Entropy is negative for the entire temperature range studied in the present work. Gibbs ' free energy increased with the increase in temperature, being its positive values. [ABSTRACT FROM AUTHOR]