For practical purposes, you'll want to look at about 2 compression ratios (i.e., for the 20 psia exhaust you'll only be able to pull the suction down to about 10 psia). if you're exhausting into 20 psia, you'll need something over 40 psia steam).

For scoping evaluation, you'll need something like twice the steam pressure as your exhaust pressure (i.e. It sounds like you're in the market for an 'ejector'. If you are trying to compress a gas then you don't want to use an eductor (the effeciencies are too low, I've done it but it requires a lot of power fluid). The reason for the lecture is that if you a trying to pump liquid you don't want to use and ejector (velocities get pretty high). Steam can be used as the motive fluid in either case. The throat has a very short entry transition and a straight section followed by a divergent section.Īn ejector is intended to move high gas-cut fluids and has a convergent section for an entry to the straight throat which is again followed by a divergent section. They're all in the same family, but they're each a different beast.Īn eductor is a device intended to move high liquid-cut fluids.

RE: Eductor calculations codeeng (Petroleum) 17 May 05 10:34Įductors, Ejectors, Jet Pumps, hose-end sprayers, and sand blasters are all in the family of equipment called 'thermocompresors'. The two then exit the eductor at an intermediate pressure.Īlso, any good sites that thoroughly explain steam usage in refineries? I am looking for something that starts with the basics of steam. This in turn sucks the stack gas into the eductor. The pressure of the motive stream is dropped, to increase its velocity. This flow will serve as a 'fast loop' that every so often an analyzer will pull a 'slip stream' from to test.Īny suggestions as to how to formulate a relation of motive stream to outlet pressure? The eductor used for gases is basically a converging/diverging nozzle from what I understand. The outlet of the eductor will have a stack gas/steam mixture that will then be returned to the stack. We are passing the steam at some pressure (this is what is to be determined) through the eductor to induce the flow of a stack gas, which is at or near atmospheric pressure (may actually be a slight vacuum).

The question is what pressure can we regulate this steam to in order to still maintain the flow. We have up to a 150# steam supply as the motive stream. I am a new engineer and am looking for pointers on calculating the flowrate needed to move a gas.

Ejector design calculation software