Numerical modeling of radiative heat and mass transfer for sweet potato during drying

Abstract

In this study, a numerical model was developed to accurately describe the changes in moisture content and temperature distribution of sweet potato during infrared drying, with the consideration of shrinkage-dependent diffusivity and evaporation phenomena. The couple heat and mass transfer and 2D axisymmetric simulations were done using COMSOL Multiphysics. The simulation results were further evaluated based on experimental data. Sensitivity analysis was also conducted and the effects of different simulation parameters on the drying process were presented. The results showed that the developed model considering shrinkage diffusivity and evaporation adequately described the drying process of sweet potato undergoing infrared drying. The mass transfer coefficient, heat transfer coefficient, shrinkage-dependent diffusivity, and infrared heat energy greatly influenced the moisture distribution during the drying process of sweet potato. The temperature distribution during the infrared drying of sweet potato was highly sensitive to the infrared heating energy. Practical applications: Sweet potato is a common industrial crop with numerous human benefits. Industrial drying of sweet potato using conventional methods is energy intense translating into higher production cost. Infrared drying has been reported to consume less amount of energy compared to other thermal drying processes. However, this drying method has also shown to affect the quality of dried product owning to its high and nonuniform temperature distribution. In this study, heat and mass transfer during infrared drying was analyzed and modeled. The simple model was able to predict the temperature and moisture distribution during drying. Consequently, the heat and mass transfer model will be useful in controlling and optimizing the infrared drying process and improve the final quality of sweet potato.