The most common motive fluid is steam at 80 PSIG (6 bar abs.) to 400 PSIG (28 bar abs.). More pressure rise occurs along the discharge cone as flow slows down. A stationary sonic shock wave forms in the throat of the diffuser, and absolute pressure rises sharply at this point. These systems are ideally suited to high vacuum applications but are only marginally useful as compressors.Ī jet of motive fluid is supersonic velocity entrains the inlet stream and raises its velocity to the speed of sound as the two flows mix.
Therefore, ejectors are better suited to handling gases with low molecular weights and when operating at low absolute pressures. An ejector operates on a mass basis, not by displacing volume. The nozzle controls the expansion of steam and converts pressure into velocity thus, creating a vacuum to transfer gases. Steam ejectors pass steam through an expanding nozzle. NASH steam jet and air ejectors minimize greenhouse gas emissions and operational efficiency while improving system stability. Application engineers ensure maximum efficiency and performance benefits while optimizing a hybrid system customized to processes, applications, and technology requirements. Nash is globally recognized for assembling the most efficient steam jet and air ejectors and ejector vacuum systems. Steam ejectors can also be combined with liquid ring vacuum pumps to create a hybrid capable of deep vacuum that ejectors can deliver but with lower energy use. Air jets of this type are convenient because no steam or pressurized air source is required to make it work, just the vacuum pump. This is often used in applications such as deaeration when the vacuum system must be able to pull down to the vapor pressure of the water that is being degassed. When paired with a NASH liquid ring vacuum pump, they can use the air from the room or the pump exhaust as motive air to increase the vacuum level the pump is capable of reaching. Air is often employed on small ejectors when steam is not available.
The resulting mixture enters the diffuser where velocity energy is converted to pressure at the ejector discharge.Įjectors that use air as motive are often called air ejectors or air jets. The jet of high-velocity steam or gas entrains the gas to be evacuated or pumped in the suction of the ejector. The steam or air converts that pressure or potential energy to velocity or kinetic energy. In a jet or ejector, a relatively high-pressure gas, like steam or air, expands through a nozzle. Steam ejectors use steam or gas instead of moving parts to compress a gas. Steam Ejector & Hybrid Vacuum System Technology
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