Simplified model for heat and mass transfer during primary drying of dual-chamber cartridge with shell holder

Dual-chamber cartridge (DDC) offers convenient reconstitution for freeze-dried products. To ensure product quality and reduce dry time, simplified model on DDC heat and mass transfer during primary drying is essential for off-line optimization and on-line monitoring. In this paper, a simplified heat and mass transfer model for primary drying stage of DDC with shell holder was proposed based on rarefied gas heat transfer model and lumped heat capacity model. Effect of rarefied gas flow and heat transfer, gap distance, chamber pressure and shelf temperature on DDC heat and mass transfer characteristics were analyzed. The results showed that simplified model could quickly predict product temperature accurately, but sublimation rate predictions showed 13.5 % deviation due to lumped heat capacity assumption. Rarefied gas conduction in the gap between shell holder and cartridge is the dominant heat transfer mechanism. Low gap distance and high shelf temperature correspond to high rarefied gas heat transfer, improving mass transfer rate and reducing dry time. Optimal chamber pressure exists for optimal heat and mass transfer due to varying dominate effect of rarefied gas heat transfer and vapor flow driving force. The proposed simplified model could provide valuable insights into structural design and process control for enhanced DDC heat and mass transfer.