×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

calculating pressures in split flow from a compressor

calculating pressures in split flow from a compressor

calculating pressures in split flow from a compressor

(OP)
Hi,

I have an NPK09 24v DC air compressor attached to which I have 4mm inner diameter tubing split into 3 then these tubes are split into 3 again leaving 9 4mm inner diameter outlet tubes (see diagram). I wish to calculate the theoretical mass flow rates, exit pressures and hence force exerted by the air stream at these outlets as I will eventually be using each of these nine outlets to displace a 1 gram mass. What I ultimately want to achieve is to determine the minimum volumetric flow rate and pressure delivered from the pump that will still allow me to vertically displace this mass when placed on one of these outlets.

So far I have calculated that, at a delivery of 15 l/min and hence pressure of 1 atm (see attached data sheet for the npk 09 pump);
volumetric flow rate = 2.5x10^-4 m^3s^-1
air velocity from pump = 4.97ms^-1
mach number - 0.0145 << 1 hence assume incompressible flow
I am assuming dry, inviscid and newtonian 20 degrees c air

Can I use the bernoulli equation to calculate Pe, the pressure at the outlet tubes?

Am I right in saying the sum of the mass flow rates through the outlet tubes = the mass flow rate in?

Once I have pressure and mass flow rate can I use this equation to find the force at the outlet tubes - F = mdot * ve + (Pe - Pat)*A, where Pat is atmospheric pressure, A is the CSA of the tube, mdot is mass flow rate and ve is exit velocity.

What other assumptions must I make?

Cheers for any help.

RE: calculating pressures in split flow from a compressor

I think you're correct, theoretically. The problem will come as you attempt to keep the pipe outflows balanced. I think the weights will not displace equally and possibly have an effect on outlet pressures of each discharge pipe, which will have an effect on the inlet pressures and flows going into each outlet pipe. I don't have a good feeling about trying to maintain all 9 outlets at equal flows and pressures with weights. It's hard enough, if not nearly impossible, to do it with needle valves.

Independent events are seldomly independent.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources