Experimental and theoretical investigation of drying behaviour of garlic in an inert medium fluidized bed assisted by microwave

Although many investigations have been carried out on the modeling of microwave heating and obtaining the temperature distribution in the foodstuffs exposed to microwave radiation, little detailed analysis is available in the literature on the experimental and mathematical modeling of simultaneous heat and mass transfer in combined microwave-convective drying systems. In this study drying behaviour of garlic was investigated in a microwave assisted fluidized bed dryer containing some inert particles. A pilot-scale microwave assisted fluidized bed dryer was set up for this purpose. Glass beads particles were used as inert materials. Based on the simultaneous heat and mass transfer, a mathematical model was proposed for predicting the temperature and moisture distribution in the drying sample, applying the Lambert’s law, as microwave absorption relationship. The heat loss due to surface evaporative cooling was also considered at the external boundaries. A numerical solution was developed for the proposed model using an implicit finite difference method in one dimensional system. The model was validated by comparing the calculated data with the experimental data, obtained for garlic of different sizes during drying. The effects of microwave power density and also drying air temperature were investigated and discussed.