The steam generated in the heating chamber carries a large amount of liquid droplets. Upon entering the larger evaporation chamber, these liquid droplets are separated from the steam through self-condensation or the action of a demister. Typically, the demister is located at the top of the evaporation chamber.
Evaporators are classified into three types according to operating pressure: atmospheric pressure, pressurized, and depressurized. They are also classified according to the movement of the solution within the evaporator: ① Circulating type: The boiling solution passes through the heating surface multiple times in the heating chamber, such as central circulation pipe type, suspended basket type, external heating type, Levin type, and forced circulation type. ② Single-pass type: The boiling solution passes through the heating surface once in the heating chamber without circulation, and the concentrated liquid is immediately discharged, such as rising film type, falling film type, stirred thin film type, and centrifugal thin film type. ③ Direct contact type: The heating medium directly contacts the solution for heat transfer, such as the submerged combustion evaporator. Evaporation devices consume a large amount of heating steam during operation. To save heating steam, multi-effect evaporators and vapor recompression evaporators can be used. Evaporators are widely used in chemical, light industry, and other sectors.
In medicine, vaporizers are used to evaporate volatile inhaled anesthetics, which are liquid at room temperature. Vaporizers effectively evaporate these liquid anesthetics into gas and precisely regulate the concentration of the vapor output. Evaporation requires heat, and the temperature around the vaporizer is the primary factor determining the evaporation rate. Modern anesthesia machines widely employ temperature-flow-compensated vaporizers, which automatically compensate for changes in temperature or fresh gas flow to maintain a constant evaporation rate, ensuring a stable output concentration of the inhaled anesthetic leaving the vaporizer. Because different volatile inhaled anesthetics have different boiling points and saturated vapor pressures, vaporizers are drug-specific; for example, enflurane vaporizers and isoflurane vaporizers are not interchangeable. In modern anesthesia machines, the vaporizer is usually placed outside the anesthesia breathing circuit and connected to a separate oxygen flow. The evaporated inhaled anesthetic vapor is mixed with the main airflow before being inhaled by the patient.
