Article Highlights

• The sweet potato slices are forced convection dried by hot air in tunnel dryer • The drying models are investigated at different conditions • The effective diffusivities and activation energy are estimated In order to investigate the transfer characteristics of the sweet potato drying process, a laboratory convective hot air dryer was applied to study the effects 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 fitted with mathematical models, and the effective diffusion coef-ficients were calculated. The results 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 was found to be the most satisfactory for velocity and thick-ness. 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 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