Motive fuel gas consumption for Ejectors

[Sawsan311]

Dear All,

I understand the principle of ejector is based on bernoulli equation and conversion of pressure energy to kinetic energy. I need to roughly estimate the requirement of 16 barg fuel motive gas for an ejector installed on a tank, is there any available rules of thumb/equations

thanks

regards,

 

[EdStainless]

There are sizing equations on the web sites of people that make eductors (such as Fox).
The motive fluid maters (density, vapor pressure, flow and head) as well as what is being carried.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[EmmanuelTop]

Check manufacturer's website, they offer tools for steam jet calculations.

See also

https://www.graham-mfg.com/usr/pdf/TechLibVacuum/218.PDF

https://www.graham-mfg.com/usr/pdf/TechLibVacuum/24.PDF

There is no such thing as "common sense" - Apollo RCA

 

[Sawsan311]

Thank you all for your great inputs,

I have one through the below thread and I could see the following:

https://croll.com/products-2/vacuum...olecular weight,than it will saturated vapor.

- for the same motive gas rate and pressure with the same suction pressure of the load process gas and for the same single stage ejector design, the higher the molecular weight of the load gas, the greater is the ejector capacity. In other words, for the same capacity, less amount of motive gas is required for a higher MW load gas. Can we interpret this finding by the density difference between the motive gas fluid and the load gas process fluid? And hence better entrainment in the inlet chamber?

- For the same ejector design, same suction pressure on load side, if the motive gas pressure is increased, the capacity of the ejector decreases, what is the reasoning behind this finding? is it due to more instabilities causing pressure to exceed the break up pressure? or at that point we will have leakage flow of high pressure motive into the tank rather than directed into the diffuser section?

Appreciate your views on the interpretation of the above findings...
thanks

regards,

 

[Compositepro]

Yes, for higher gas density more mass rate can pass through the diffuser nozzle.

At a certain point increasing motive gas flow will exceed the capacity of the diffuser section and it will back up into the suction.

 

[pierreick]

Hi,
Consider the book in reference (bible): Steam ejectors for the process industries by Robert B.Power
Good luck
Pierre