Results 1 to 7 of 7
  1. #1
    Join Date
    May 2012
    Location
    Nebraska
    Posts
    25

    compression ratio

    For my 19DK chiller: to find compression ratio of this system which operates in a vacuum (R-11), typically 14"hgVAC with 7 psig head, can I use this formula: comp ratio=head pressure +14.7 divided by suction pressure + 14.7?

  2. #2
    Join Date
    Jul 2005
    Posts
    5,153
    Quote Originally Posted by tpodany88 View Post
    For my 19DK chiller: to find compression ratio of this system which operates in a vacuum (R-11), typically 14"hgVAC with 7 psig head, can I use this formula: comp ratio=head pressure +14.7 divided by suction pressure + 14.7?
    21.7psia/6.9 psia=3.14 compression ratio. If you have digital gauges then just switch to absolute pressure units, such as psia, then you can enter those directly in the equation. Compression ratio is the ratio of absolute pressures. HTH.

  3. #3
    Join Date
    Mar 2007
    Posts
    3,058
    You first have to convert inches of mercury to PSIG by multiplying by .491. Then, you can add 14.7 to both discharge and suction to obtain PSIA for both. Divide suction into discharge and you have your compression ratio.
    "There is no greater inequality than the equal treatment of unequals."

    -Thomas Jefferson

  4. #4
    Join Date
    Jul 2005
    Posts
    5,153
    Quote Originally Posted by hvacrmedic View Post
    21.7psia/6.9 psia=3.14 compression ratio. If you have digital gauges then just switch to absolute pressure units, such as psia, then you can enter those directly in the equation. Compression ratio is the ratio of absolute pressures. HTH.
    Sorry, I forgot to subtract my converted low side pressure from the atmospheric pressure . 14 in hg = 6.9 psi, not 6.9 psia, and is measured relative to 0 psig, not 0 psia. 0 psig in turn is equal to 14.7 psia. So the low side absolute pressure is given by 14.7 psia - 6.9 psi = 7.8 psia.

    So the compression ratio was actually 21.7/7.8 = 2.78

  5. #5
    Join Date
    May 2012
    Location
    Nebraska
    Posts
    25
    Thanks!

  6. #6
    Join Date
    Apr 2010
    Location
    Ontario
    Posts
    12
    hu compression ratio on a centrifugal compressor? Thought it had more to do with stroke and volume.Or maybe not but got me thinking

  7. #7
    Join Date
    Apr 2010
    Location
    Ontario
    Posts
    12
    O Ya its more to do with impeller lift and gas velocity

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event