Page 2 of 2 FirstFirst 12
Results 14 to 17 of 17
  1. #14
    Join Date
    Jun 2009
    Location
    StL, MO
    Posts
    572
    This can be done with kitControl math blocks and a little help from excel's Trendline feature. Copy and paste the temperature vs pressure values in to excel. Convert to PSIA and Deg R (curve fitting works better). Create a graph and try the various Trendlines until you get a good fit. I came up with this for R134a. y = 0.00003561 x^3 - 0.01308796 x^2 + 2.12259171 x + 421.11910836 With x = PSIA and a range of 20.7 to 149.7 and y = deg R.
    Name:  R134a.jpg
Views: 178
Size:  42.4 KB
    UA LU 562

  2. #15
    Join Date
    Jul 2010
    Location
    Az
    Posts
    73
    Could I get a copy of the program objects also, email is in my profile, Thank you.

  3. #16
    Join Date
    Jul 2008
    Posts
    1,413
    Quote Originally Posted by DaveCR View Post
    I came up with this for R134a. y = 0.00003561 x^3 - 0.01308796 x^2 + 2.12259171 x + 421.11910836 ]
    nice work ... though I think it maybe time to make a generic curve-fit Program Object to the 4th or 5th order.

    ...maybe even have an Enum setting for different refrigerants
    1 + 1 = 3 ( *** for very large values of 1)

    ...everybody wants a box of chocolates and long stemmed rose

  4. #17
    Join Date
    Jun 2009
    Location
    StL, MO
    Posts
    572
    Thanks. For 134a:
    y = 9.20621E-10 x^5 - 6.26875E-07 x^4 + 1.65989E-04 x^3 - 2.26106E-02 x^2 + 2.14070E+00 x - 1.32707E+01
    Input pressure range (PSIA) 14.7 to 244.7. Output R. This turns out to be quite a good fit with R squared = 0.9999
    Last edited by DaveCR; 01-27-2013 at 10:44 AM. Reason: punctuation
    UA LU 562

Page 2 of 2 FirstFirst 12

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