An Efficient Calculation of Multidimensional Freeze-Drying Problems Using Fixed Grid Method

Abstract

A calculation procedure based on a fixed grid method streamlined for multidimensional freeze-drying problems was developed, considering coupled heat and mass transfer, sublimation of ice, and motion of ice front. Efficiency of the fixed grid calculation in solving one- and two-dimensional freeze-drying problems was evaluated by comparing its accuracy and calculation cost with those of a conventional moving grid calculation. The numerical investigation showed that the fixed grid method can produce accurate results comparable to those obtained by the moving grid method, with almost equal calculation cost in case of one-dimensional freeze-drying problems. But the fixed grid method required about 70% more computation time than the moving grid method in case of two-dimensional freeze-drying problems. It is thought that the fixed grid method may be advantageous over conventional moving grid methods when freeze-drying problems involving cumbersome moving interface geometries have to be considered.

Keywords:

• Freeze-drying
• Numerical analysis
• Finite volume method
• Fixed grid method
• Moving grid method