×
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

Dry Air Calculations for Work of Compression

Dry Air Calculations for Work of Compression

Dry Air Calculations for Work of Compression

(OP)
I am sizing up air flasks for a piston accumulator.  The purpose of the accumulator is to capture a large volume of liquid (glycol) which is exhausted through an upstream valve in our process. The gas side of the piston will be charged with dry air (I have been told the air quality must be based on a dewpoint of -10 degrees F or lower). The initial charge on the air (and the entire system) will be approximately 400 psig. During the fluid accumulation, the pressure will rise to about 650 psig in a matter of  about 3 seconds.  I am assuming an adiabatic compression on the airside.  

Now to the question – for the purpose of future energy balance calculations, I cannot find any equations which takes air quality (dryness) into account when calculating the work required to compress a volume of air, yet I know it requires more work to compress saturated air vs. dry air.  Can anyone advise on this or lead me to a reference for this type of calc? Standard thermo or fluids texts aren't helping me much.

Thanks in advance,
TC7

RE: Dry Air Calculations for Work of Compression

Should be able to get there using one of the Tds equations, second law of thermo, for adiabatic, dS = dQ / T = 0.  Then you have TdS = CvdT + RT / V dV which you should be able to integrate from "uncompressed" to "compressed" state assuming that the air behaves like an ideal gas.  Use the universal gas constant and calculate the MW of the moist air for use in the equation.

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