Controlled nucleation during freezing step of freeze drying cycle using pressure differential water vapor CO₂ ice crystals

摘要

A method of controlling and enhancing the nucleation of product in a freeze dryer wherein a product is maintained at a predetermined temperature and pressure. A mixture of water vapor and CO₂ gas is introduced into a condenser chamber separate from the product chamber to create a predetermined volume of condensed frost, ice and dry ice crystals on an inner surface of the condenser chamber. The condenser chamber is connected to the product chamber and has a predetermined pressure that is greater than that of the product chamber. Upon the opening of the condenser chamber into the product chamber, gas turbulence is created that causes the condensed frost in the form of an ice fog and accompanying ice and dry ice crystals to rapidly enter the product chamber for even distribution therein to create uniform and rapid nucleation of the product in different areas of the product chamber.