Thermophysical properties and kinetic study of Dioscorea bulbifera

Abstract

This research focused on the modeling of the convective drying of aerial yam using finite element methods. The thermo-gravimetric analyzer was used to determine the thermal stability of the sample. An aerial yam sample of size 30 x 20 x 4 mm were cut with a mold designed for the purpose and dried in a convective dryer set at 4m/s fan speed and temperatures of 68.58 and 60.56 °C. The volume shrinkage of the resultant dried sample was determined by immersing the sample in a toluene solution. The finite element analysis was done with PDE tools in Matlab 2015. Seven kinetic models were employed to model the drying process. The result showed that the thermo gravimetric analysis (TGA) profile of aerial yam consisted of three regions and the maximum thermal degradation rates of the sample occurred at 432.7 °C. The effective thermal diffusivity of the sample increased as the temperature increased from 60.56°C to 68.58°C. The finite element prediction of moisture content of aerial yam at an air temperature of 68.58°C and 60.56°C shows R2 of 0.9663 and 0.9155, respectively. The results showed a good agreement between the predictions and the measurements indicating that a highly reliable finite element model was developed. The result also shows that the best kinetic model for the aerial yam under the given drying conditions was the Logarithmic model with a correlation coefficient of 0.9991.