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Computational Thermal Sciences: An International Journal
ESCI SJR: 0.249 SNIP: 0.434 CiteScore™: 1.4

ISSN Imprimer: 1940-2503
ISSN En ligne: 1940-2554

Computational Thermal Sciences: An International Journal

DOI: 10.1615/ComputThermalScien.2020026393
Forthcoming Article

Numerical and Experimental Modeling of Lyophilization of Lactose and Mannitol Water Solutions in Vials

Matjaz Hribersek
University of Maribor
Matjaz Ramsak
University of Maribor
Jurij Iljaz
University of Maribor
Jure Ravnik
University of Maribor
Matej Zadravec
University of Maribor
Matej Avanzo
LEK d.d.
Klemen Kocevar
LEK d.d.
Spela Irman
LEK d.d.
Mateja Cegnar
LEK d.d.
Iztok Golobic
University of Ljubljana
Anze Sitar
University of Ljubljana

RÉSUMÉ

The paper reports on the development of a numerical model for the simulation of a lyophilization process in a vial. The lactose and mannitol-water mixtures are used as the working medium in the vial. Experimental analysis of lyophilization dynamics inside a single vial and multiple vials in a laboratory scale lyophilizer is reported, with the main focus on the primary drying phase. The key parameter measured is the temperature distribution inside the main axis of the vial filling. In the numerical model, a 1D vial approximation is used, and governing equations of heat and water vapour transport with moving front between the frozen and the porous part of the filling are solved by a dedicated finite difference method in a time stepping nonlinear iteration procedure. A dedicated mapping is applied in order to implement the boundary conditions, derived from the axisymmetrical case, in the case of the 1D vial geometry approximation. The comparison of numerical and experimental results show, that the developed numerical model is able to accurately capture the transition points from primary to secondary drying, accompanied by accurate capturing of the temperature levels inside the drying material. The main difference in the drying of lactose and mannitol solutions lies in the fact, that the lactose shows undercooling effects during the primary drying phase, which is not the case for the mannitol solution. This effect is a consequence of shrinking behaviour of lactose porous matrix, losing contact with vial side and hence decreasing the overall heat input to the vial.