Simulation of ice deposition in a freeze dryer condenser: A computational fluid dynamics study

Abstract

The development and validation of a mechanistic model for the deposition of ice within a freeze-dryer condenser using Computational Fluid Dynamics is presented in this paper. Freeze-drying, a dehydration technique used widely in the pharmaceutical and food industries, involves the sublimation of frozen product moisture under controlled conditions. The efficiency of the condenser has a significant impact on the overall process efficiency and product quality. Therefore, a comprehensive understanding of ice deposition is essential for freeze-drying processes. The proposed condensation model integrates fundamental heat and mass transfer principles with the specific interactions that occur at the solid-vapour interface during ice deposition, and integrates it further with transport phenomena in the condenser, including fluid flow, heat and vapour transport influencing the deposition kinetics of the ice. To validate the model, experiments were conducted under controlled freeze-drying conditions, and the results compared with the results of the developed model. The numerical results fell within the confidence interval of the measured values, which shows a high degree of agreement between the model predictions and the experimental data, and confirms the reliability of the proposed approach. Using the validated model, a parametric study was also conducted, to evaluate the effects of condenser temperature, sublimation rate and the presence of inert gas on the pressures within the system and the efficiency of the deposition. The mechanistic model provides detailed insights into the ice deposition kinetics during freeze drying, and enables process engineers to optimise the condenser design and operating parameters in order to improve performance and product quality.