Simulation Strategies in Mathematical Modeling of Microwave Heating in Freeze-Drying Process

Abstract

In this article, a one-dimensional, two-region model of the primary freeze-drying process of granular materials and foodstuffs in microwave heating is formulated. This model takes into account unknown a priori sublimation temperature T_s(t) and mass concentration of water vapor C_s(t) at the moving ice front. In vacuum freeze-drying experiments, activated carbon Sorbonorit 4 (Norit Corporate, USA) was freeze dried at 2.45 GHz frequency inside the monomode brazen applicator. On the basis of measurement results and additional data for beef reported in the literature, two strategies commonly applied in process simulation were investigated. Mathematical modeling tested the adequacy of taking into consideration temperature dependency of material loss factors (first strategy) and a variety of electric field strengths during the process (second strategy). The results of comparative simulations and experimental verifications are discussed and presented in graphical form.

Keywords:

• Foodstuffs
• Granular materials
• Loss factor
• Mathematical model
• Microwave freeze drying
• Primary drying

Notes

^a Data from Ma and Peltre.^{[ 17 , 18 ]}

^a Our own measurements.

^b Computed on the basis of literature data.^{[ 17 , 18 ]}