Thermodynamics Research Center / ThermoML | International Journal of Thermophysics

ABSTRACT

PVT properties weremeasured for hydrogen by the Burnettmethod in the temperature range from 353K to 473K and at pressures up to 100MPa. In the present Burnett method, the pressure measurement was simplified by using an absolute pressure transducer instead of a differential pressure transducer, which is traditionally used. The experimental procedures become easier, but the absolute pressure transducer is set outside the constant temperature bath because of the difficulty of its use in the bath, and the data acquisition procedure is revised by taking into account the effects of the dead space in the absolute pressure transducer. The measurement uncertainties in temperature, pressure, and density are 20mK, 28kPa, and 0.07% to 0.24% (k = 2), respectively. Based on the present data and other experimental data at low temperatures, a virial equation of state (EOS) from 220K to 473K and up to 100MPa was developed for hydrogen with uncertainties in density of 0.15%(k = 2) at P ? 15MPa, 0.20 % at 15 MPa less than P ? 40 MPa, and 0.24 % at P greater than 40 MPa, and this EOS shows physically reasonable behavior of the second and third virial coefficients. Isochoric heat capacities were also calculated from the virial EOS and were compared with the latest EOS of hydrogen. The calculated isochoric heat capacities agree well with the latest EOS within 0.5% above 300K and up to 100MPa, while at lower temperatures, as the pressure increases, the deviations become larger (up to 1.5 %).