Control of freezing as a mean for process intensification in freeze-drying

The Vacuum Induced Nucleation method is here proposed as a mean to promote the uniformity of the batch and make the process more energy efficient. A deeper investigation on the nucleation event is also addressed. Product structure was analysed to evaluate inter-vial homogeneity, while the increasing in product temperature, when ice-nucleation occurs, was monitored by using thin film thermocouples sputtered on the outer surface of the vials in order to address a non-invasive temperature measurement. The mass transfer resistance values were found to change with freezing conditions; these values were used to calculate the design space and to simulate the process in order to highlight the cycle duration reduction with freezing control.