Simulation of a Controlled Freeze-Drying Process

Abstract

This work contains the basic theory of the coupled mass and heat transfer occurring during the primary drying portion of a lyophilization process. A mathematical model for the entire freezedryer is derived, which accounts for all of the essential effects occurring during the primary drying of a batch freeze-drying process. The describing equations are solved numerically and a variety of simulations are done to investigate the behaviour of the system, such as the role of the pore radius and the influence of the initial temperature. The influence of the inert gas inside the drying chamber is examined. Future effects and difficulties are shown, such as the procedure of determining the temperature at the interface front by closing the valve between the drying chamber and the condenser.

Key Words:

• Lyophilization
• mass and heat transfer
• mathematical model
• condenser valve simulation

Additional information

Notes on contributors

M.P. Schoen

Prof. Raymond P. Jefferis III, Professor of Engineering at Widener University, Chester, PA, USA, has been involved with the instrumentation and control of pharmaceutical fermentation and lyophilization processes since 1971. He is a member of the International Society of Pharmaceutical Engineers (ISPE) and serves on its Education Committee. His recent activities have been in the application of computational fluid dynamics to pharmaceutical cleanroom design.

R.P. Jefferis

Dr. Marco P. Schoen holds a Ph.D. in engineering mechanics from the Old Dominion University, an M.E. in mechanical engineering from Widener University, and a B.Sc. degree in mechanical engineering from the Swiss College of Engineering. He is currently an Associate Professor of mechanical engineering and the director of the Applied Research Center (ARC)at the Indiana Institute of Technology. Dr. Schoen performs research in the areas of system identification and controls of flexible structures, magnetic suspension systems, mobile robot positioning systems, wave-energy device systems in irregular waters, biomedical systems, and in the area of modelling and simulation of pharmaceutical processes.