ejector

An ejector is a device that uses the momentum of a high-velocity driving fluid to entrain and move a second fluid. By converting energy from the driver fluid through a converging nozzle and mixing chamber, the ejector creates a low-pressure region that draws in the suction fluid, and the two streams are discharged together as a mixed flow. Because it relies on fluid dynamics rather than moving mechanical parts, an ejector can operate with minimal maintenance.

Common types include steam jet ejectors, air ejectors, and water or gas jet ejectors. The driving fluid may be steam, compressed air, or another gas, while the process fluid can be a gas or vapor. Performance depends on the desired suction pressure, the properties of the fluids, and the allowable back pressure on the exhaust side.

Applications are widespread in industrial processing. Ejectors generate vacuum for distillation, evaporation, drying, and condenser priming in power plants. They are used for degassing and vapor handling in chemical and petrochemical plants and find roles in certain refrigeration and wastewater treatment contexts. Ejectors can serve as compact, low-maintenance alternatives to mechanical vacuum pumps in appropriate service conditions.

Limitations include relatively moderate efficiency and sensitivity to operating conditions. The effectiveness of an ejector is influenced by back pressure, the properties of the driving and process fluids, and the presence of impurities or particulates. Because they have no moving parts, ejectors require proper control of the driving fluid supply and suitable piping to maintain stable operation.