how to find suction pressure in ejector
how to find suction pressure in ejector
(OP)
hi guys have just joined the forum ,i have a problem -i need to find out suction pressure in an ejector with following data
load fluid flow rate 1931 kg/hr(air pressure 1.012 kg/sq cm abs)
motive fluid flow rate(steam 4.8 kg/sq cm abs) 1448kg/hr
discharge pressure 1.24 kg/sq cm abs
can i apply equations for converging diverging nozzle for finding it out
load fluid flow rate 1931 kg/hr(air pressure 1.012 kg/sq cm abs)
motive fluid flow rate(steam 4.8 kg/sq cm abs) 1448kg/hr
discharge pressure 1.24 kg/sq cm abs
can i apply equations for converging diverging nozzle for finding it out





RE: how to find suction pressure in ejector
I designed an ejector earlier this month. I used an old FORTRAN program that I purchased from IHS. I did the preliminary sizing with a VBA program I wrote using sub-sonic nozzle arithmetic (i.e., based on Bernoulli). The FORTRAN result had little comparison to the output of my VBA program. We'll be building this gadget in the next few weeks and then we'll see which program came closer. Earlier this year I designed and built an ejector using the same programs--the FORTRAN predicted values that were within 5% of measured parameters and my VBA program was over 35% off.
The short answer is that I've always found it impossible to predict performance on an ejector that someone else designed, there are just too many "small" things that make a huge difference in performance.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
The main difference beteen humans and apes is that we have cooler tools
RE: how to find suction pressure in ejector
also, is there any way to find out how much air will produce same suction as steam
air pressure 7 kg/sqcm
steam 4.8kg/sq cm
i know it has to be roughly arnd 1.4 times but i need to be a bit more accurate...and lastly how can i possibly find optimum temperature for motive fluid
RE: how to find suction pressure in ejector
David
RE: how to find suction pressure in ejector
I can't find anything about multi nozzle ejectors...can a 3 nozzle ejector maintain a vacuum of 40 mm Hg with entrainment ratio 1.65.
RE: how to find suction pressure in ejector
I suggest that the best thing you could do is to contact one of the experienced ejector manufacturers like say Croll-Reynolds at www.croll.com
Milton Beychok
(Visit me at www.air-dispersion.com)
.
RE: how to find suction pressure in ejector
It's all you. I haven't gotten through to him, maybe you'll have better luck.
David
RE: how to find suction pressure in ejector
I2I
RE: how to find suction pressure in ejector
Good luck with it.
David
RE: how to find suction pressure in ejector
However, short-cut methods have been published which allow you to make estimates - even if they are not good enough to manufacture from. A graphical method is included in Perry (Chemical Engineers Handbook). I only have access to a 1963 4th Ed where I am at the moment and in that version it is on pages 6-30 to 6-32. That method does include a way to predict how much air you would need as motive fluid in the place of steam. A critical factor that you have not mentioned is the ratio of the areas of the motive nozzle and the venturi throat. You will have to measure this to be able to make the prediction you need.
Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com