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


How to calculate vaccum pressure ?

How to calculate vaccum pressure ?

How to calculate vaccum pressure ?

Dear all,

I am having a 12 mm diameter piston and cylinder arrangement,Using a handle i am moving the piston upward for 35 mm for inflow of fluid from reservoir against a check valve.
My question is how much partial vacuum pressure is created in the cylinder for the rise of 35 mm movement of 12 diameter piston?
Please provide any formula or sample calculation.

thanks in advance.

RE: How to calculate vaccum pressure ?

Assuming that the system is leak free, you can use Boyle's law to calculate the air pressure in the bigger volume...

RE: How to calculate vaccum pressure ?

With a liquid you should get close to a perfect vacuum (or the vapor pressure of the liquid) minus the cracking pressure of the check valve. For a gas it all depends on the "head space" between the piston and the check valve. The gas in this space will be expanded as the piston moves. If you double the volume, the pressure will be half an atmosphere.

RE: How to calculate vaccum pressure ?

What do you mean by fluid? a liquid or a gas? If a liquid, some of that will turn into a gas during a vacuum; if the fluid is a gas then boyle's law could be an adequate approximation.

RE: How to calculate vaccum pressure ?

I'll rephrase "... If a liquid, some of that will turn into a gas or vapor during a vacuum"

RE: How to calculate vaccum pressure ?

Does't the density of the fluid matter in this?

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!


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