Freeze dryers consist of a few sub-systems: refrigeration system, vacuum system, control system, product chamber and condenser. The refrigeration system cools the condenser located in drying chamber. It also cools shelves in the product chamber to freeze the product. The vacuum system consists of one or several vacuum pumps which connected to an airtight condenser and attached product chamber. Control systems vary in complexity and typically include temperature and pressure sensing. Product chamber is typically a larger chamber with shelves/trays on which the product is dried. The drying chamber is a horizontal cylindrical or rectangular pressure container, containing the condenser, which is installed close to the trays. The products are placed on the trays and heat is supplied through radiation or conduction. The condenser attracts the vapors being sublimed off the product and condenses them back into solid form (ice). The ice condenser can be located inside the drying chamber or in a separate chamber (external condenser) connected to the product chamber by a vapor port.
Batch freeze dryers are popular in market, with capacities ranging from 10 kg to 2000 kg per batch are common.