×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Calculating hydrogen gas discharge flow from a pipe opening

Calculating hydrogen gas discharge flow from a pipe opening

Calculating hydrogen gas discharge flow from a pipe opening

(OP)
I trying to find a quick way to calculate the actual flow rate of hydrogen gas at the discharge point of a 1/8" (0.3175cm) pipe, if the pressure drop is from 74.7psi (515Pa) to 14.7psi (101.4Pa ambient air pressure).  The compressed hydrogen gas is at normal room temperature.

RE: Calculating hydrogen gas discharge flow from a pipe opening

How long is the tube?  If you want a quick absolute maximum limit, assume energy conservation (Bernoulli) and convert all the pressure to velocity.

Matt

RE: Calculating hydrogen gas discharge flow from a pipe opening

(OP)
In answer to mbt22
The pipe is 10cm long. I am not sure what you mean with converting all the pressure to velocity.

RE: Calculating hydrogen gas discharge flow from a pipe opening


Base on critical velocity (which you don't want to pass)
The max flow is ~3lb/hr
BTW most of the pressure drop is probably at your valve.
 

RE: Calculating hydrogen gas discharge flow from a pipe opening

(OP)
What equation or reference did you use? 3 lbs of hydrogen gas (H2) occupies a volume of about 15,000L. One Mole of H2 = 2g, which will occupy 22.4 liters as stp. One pound = 0.453592kg
Doesn't temperature AND pressure play a role if you go from a compresed gas @ 60 psi (gauge) to atmospheric pressure?

RE: Calculating hydrogen gas discharge flow from a pipe opening

Assuming choked flow at your valve the mass flow rate will be a function of the upstream pressure only (you said the upstream temp is room temp).

RE: Calculating hydrogen gas discharge flow from a pipe opening

(OP)
Which function or reference would you use to calculate the mass flow rate at constant pressure but different orifice sizes?

RE: Calculating hydrogen gas discharge flow from a pipe opening

Choked flow

M=C*A*{k*ρ*P(2/k+1)^[(k+1)/(k-1)]}^0.5

K(H2)=1.410

Minimum P/Pd  required for H2 choked flow = 1.899

M= mass flow rate, kg/s
C = discharge coefficient, dimensionless (~0.62)
A = discharge hole cross-sectional area, m²
k = cp/cv of the gas
cp = specific heat of the gas at constant pressure
cv = specific heat of the gas at constant volume
ρ = real gas density at P and T, kg/m³
P = absolute upstream pressure of the gas, Pa
Pd = absolute downstream gas pressure

good luck

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close