×
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

How To Calculate Time To Fill Gas In Closed Vessel

How To Calculate Time To Fill Gas In Closed Vessel

How To Calculate Time To Fill Gas In Closed Vessel

(OP)
Hi all
I want to derive equation to determine time to fill gas in closed vessel.
- Gas will feed to vessel with constant pressure at P1.
- Gas will feed to vessel until pressure vessel reach to feed pressure Pi-->P
- Time to fill gas in vessel until pressure vessel = feed pressur is required.

I can derive equation by using "law of conservation of mass" as below;

rho*v1*Apipe = [Vt*Mw/(ZRT)]*d(P-Pi)/dt

but I cannot find the function of v1 with differential pressure between P1 and P.

Anyone please kindly help me to clarify how to determine the function of feed gas velocity with pressure drop of (P1-P)

Thank you for your kindly help.

RE: How To Calculate Time To Fill Gas In Closed Vessel

Dang this sounds like a school problem.  I'm going to roll the dice and assume that it isn't.

You have two distinct filling periods:  (1) while P1 > P(c) (see FAQ378-1201: Mass flow rate of a gas through an orifice during choked conditions for a good discussion of choked flow and critical pressure); (2) when the two pressures are too close together to give you choked flow.

The first time period is really easy to calculate fill rate and resulting pressure, velocity is sonic and mass flow rate is a function of P1.

After the tank pressure reaches P(c), your first-principles approach fails miserably and you have to resort to empirical equations.  Take a look at Crane Technical Paper 410 for the necessary equations.

On the other hand, if your vessel final pressure is less than P(c) then the whole process is very straight forward.  Just determine the mass of gas that represents your final pressure and divide that by the mass flow rate since it is constant for sonic velocity with a constant upstream pressure.

David  

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