Evaluation of the mass transfer process on thin layer drying of papaya seeds from the perspective of diffusive models

Abstract

The mass transfer process that occurs in the thin layer drying of papaya seeds was studied under different conditions. The external mass transfer resistance and the dependence of effective diffusivity (D EFF ) in relation to the moisture ratio ( $$ \overline{MR} $$ ) and temperature (T) were investigated from the perspective of diffusive models. It was verified that the effective diffusivity was affected by the moisture content and temperature. A new correlation was proposed for drying of papaya seeds in order to describe these influences. Regarding the use of diffusive models, the results showed that, at conditions of low drying rates (T ≤ 70 °C), the external mass transfer resistance, as well as the dependence of the effective diffusivity with respect to the temperature and moisture content should be considered. At high drying rates (T > 90 °C), the dependence of the effective diffusivity with respect to the temperature and moisture content can be neglected, but the external mass transfer resistance was still considerable in the range of air velocities used in this work.