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Joule Thompson Effect

  1. Oct 4, 2008 #1
    Hey all, I'm not sure this is a homework problem, more a problem I'm having with equations and this effect.

    Experimentally we measured dT and dp, I plotted them, then determined the Joule Thompson coefficients for 3 gases (He, CO2, N2). These values came out to be

    μJT(CO2) = .815 bar/K
    μJT(N2) = .1319 bar/K
    μJT(He) = -.0949 bar/K

    which seemed reasonable enough to me.

    Now, I need to calculate theoretical values using various equations of state. I began with van der Waals, and got

    μJT = 1/Cp((2a/RT)-b)

    I thought this would be simple, just looking up the Cp, and using known van der Waals coefficients, but my calculation for CO2 comes out to be something like -4 or so, so something is wrong, but I can't figure out what it is. Also, I could not find anywhere theoretical μJT values, which I am supposed to put in my lab report.

    Thanks for any tips!
  2. jcsd
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