Modeling of Freeze-Drying of Coffee Solution using Arbitrary-Lagrangian-Eulerian (ALE) Method

C. Anandharamakrishnan, R. Deepak, N. Chhanwal, and K.S.M.S. Raghavarao
CFTRI, Mysore, Karnataka, India

Freeze-Drying is used widely in the food and pharmaceutical industries for its ability to dry thermolabile product and retain high quality. Freeze-drying involves three stage processes such as (i) freezing, (ii) primary drying and secondary drying. Modeling of primary drying is a very complex process because of the presence of a moving sublimation front whose position is determined by the heat and mass transfer rates. In this study, freeze-drying of coffee was modeled using COMSOL. The general heat transfer modes used for the temperature profile and diffusion for the moisture content. The moving mesh (at interface between ice front and dried layer) using Arbitrary-Lagrangian-Eulerian (ALE) approach to track the movement of sublimation front. The velocity of the interface was calculated using a Stefan condition at the boundary considering only conduction effects. The model predictions were validated with the experimental measurements of temperature. Progress of sublimation front with mesh movement was tracked during the freeze-drying process.