Heat transfer in vial lyophilization

Area of Science:

• Pharmaceutical Engineering
• Bioprocess Engineering
• Chemical Engineering

Background:

• Vial lyophilization is a critical process for stabilizing pharmaceutical products.
• Understanding heat transfer dynamics is essential for optimizing lyophilization cycles.
• Existing models often lack comprehensive consideration of vial geometry and environmental factors.

Purpose of the Study:

• To develop and validate a theoretical model for heat transfer in vial lyophilization.
• To investigate the influence of various parameters on heat transfer efficiency.
• To provide a foundation for optimizing freeze-drying processes.

Main Methods:

• Experimental study of heat transfer in sealed vials containing water using a pilot-scale freeze-dryer.
• Development of a dynamic, two-dimensional axisymmetric theoretical model incorporating vial and content.
• Numerical solution of differential equations based on physical models for gas thermal conductivity, conduction, and radiation.

Main Results:

• The theoretical model accurately describes heat transfer and heat accumulation in vials.
• The model successfully predicts the dynamics of corner vials by including side heat transfer.
• Vial bottom curvature, glass heat accumulation, and corner vial sidewall heat transfer significantly influence radial heat transfer.

Conclusions:

• The developed theoretical model provides a robust tool for understanding heat transfer in vial lyophilization.
• Key parameters such as vial geometry and shelf position critically affect process efficiency.
• This work lays the groundwork for improved control and optimization of pharmaceutical freeze-drying.