equation of state
Springer Online Journal Archives 1860-2000
Abstract A liquid helium state equation has been constructed for the range 1.4 to 4 K for pressures up to 25×105 Pa consistent with the known asymptotic behavior of state properties at the lamda line. It utilizes a slightly different form of state equation than used in previous studies at the lamba line, resulting in simpler expressions for all thermodynamic variables while retaining good agreement with experimental data. The amplitude ratio, A/A′, of the logarithmic term is found to be 1.14±0.03, independent of pressure, in contrast to earlier work which indicated that this ratio was pressure dependent above 15×105 Pa. The state equation can also be used to show that the entropy variation along the lama line is independent of A or A′ and to predict a finite value of Cv at the lamda line.
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