In order to investigate the transfer characteristics of the sweet potato
drying process, a laboratory convective hot air dryer was applied to study
the influences of drying temperature, hot air velocity and thickness of sweet
potato slice on the drying process. The experimental data of moisture ratio
of sweet potato slices were used to fit the mathematical models, and the
effective diffusion coefficients were calculated. The result showed that
temperature, velocity and thickness influenced the drying process
significantly. The Logarithmic model showed the best fit to experimental
drying data for temperature and the Wang and Singh model were found to be the
most satisfactory for velocity and thickness. It was also found that, with
the increase of temperature from 60 to 80?C, the effective moisture diffusion
coefficient varied from 2.962?10-10 to 4.694?10-10 m2?s-1, and it fitted the
Arrhenius equation, the activation energy was 23.29 kJ?mol-1; with the
increase of hot air velocity from 0.423 to 1.120 m?s-1, the values of
effective moisture diffusion coefficient varied from 2.877?10-10 to
3.760?10-10 m2?s-1; with the increase of thickness of sweet potato slice from
0.002 m to 0.004 m, the values of effective moisture diffusion coefficient
varied from 3.887?10-10 to 1.225?10-9 m2?s-1.