Method: Vary net vapor rate, make-up vapor (steam).
Process: Vacuum systems. Must always have vapor product.
Advantages: Easily added to systems after construction. Control valve and piping small and relatively cheap.
Disadvantages: Increases steam use and hot well water make. Increases cooling water load.
Application: Often added after-the-fact to vacuum systems for improved control.
Variants: Air or other inert gases may be used to bleed into the jet suction instead of steam.
Configuration notes: Using inert gas or air instead of steam will add a larger inert gas load to the condenser and may affect condenser operation. In multi-stage ejector systems, using non-condensable gas (air or inert gas) will load up all ejectors in the system. Steam will only load the ejector with the steam injection directly upstream.
Operation: Added load moves the vacuum jet ejector along its operating curve. The higher the load to the ejector, the higher the ejector suction pressure.
Warnings: Wet steam may cause ejector erosion from water droplets. Combination of electrical tracing, superheated steam, local water knock-out before addition to system, or other measures may be required to reduce erosion to allowable levels.
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