Water Enthalpy values
Halo, could somebody explain me, how to get (find, calculate, ...) values of enthalpy for water? (where I can find them?)
I have find this table: https://www.thermexcel.com/english/tables/eau_atm.htm
but problem is that in this tutorial:
http://www.thunderheadeng.com/downloads/petrasim/using-wells.pdf
for 6°C water they enter enthalpy = 5e4 (but enthalpy value from thermexcel.com for 6°C is 2.5e4). I am confused, how they get in tutorial enthalpy value 5e4. I have try to run simulation and it seems, that realy enthaply 5e4 is correct and 2.5e4 is wrong, because with this enthaply (2.5e4) in model water temperature is aproaching 0°C and the sollution does not converge.
Thank you,
David.
1 reply
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David,
Only briefly: I believe the discrepancy is related to the reference temperature used to calculate enthalpy. Various formulations often provide “absolute" enthalpies, which must be normalized to a reference temperature. When TOUGH says U(T) = CvT, it actually means U(T) = Cv(T - T0), where T0 = 0.0 C. This choice of T0, while arbitrary, is completely correct as long as all energies (and derived quantities) are also referenced to T0 = 0.0 C. The reference states all cancel out as long as every relationship is derived with T0 = 0.0 C
Stefan