Snoop06
- 20
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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!
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!