Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Specific Heat Constant Volume Question

  1. Apr 6, 2007 #1
    Can someone give me the equation to calculate the change of Cv (specific heat at constant volume with change in temperature.

    For example the equation to do this with Cp (specific heat at constant pressure) is:

    Cp = 1.9327e-10*T^4 - 7.9999e-7*T^3 + 1.1407e-3*T^2 - 4.4890e-1*T + 1.0575e+3


  2. jcsd
  3. Apr 6, 2007 #2


    User Avatar
    Homework Helper
    Gold Member

    Look up the equation for the given substance in a table. For example, Perry's Chemical Engineering Handbook. What substance is the equation for cp valid for? If it's an ideal gas, you can use the ideal gas constant to get a relationship between cp and cv.
  4. Apr 6, 2007 #3
    Sorry, forgot to mention the gas is air.

    Yeah, I can get Cv once I know Cp, by subtracting R:

    Cv = Cp - R.

    I was just wondering if there was an equation because I want to use it in a spreadsheet.


  5. Apr 6, 2007 #4


    User Avatar

    and the air isn't frozen, nor superheated to some obscene temperature, right? then, is not [itex]C_v[/itex], [itex]C_p[/itex], and [itex]R[/itex] constant with repect to [itex]T[/itex]? i don't follow the premise to your original question.
  6. Apr 6, 2007 #5
    Cp= Cv + R
  7. Apr 6, 2007 #6


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hi Gordon,
    Attached is the output from a spreadsheet that gives Cv and Cp at various pressures and temperatures. Just do a curve fit.

    Edit: Pressure in PSIA

    Attached Files:

    • air.zip
      File size:
      4.4 KB
    Last edited: Apr 6, 2007
  8. Apr 6, 2007 #7
    Thanks, Q.

    What is the underlying equation?


Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Specific Heat Constant Volume Question