Computational and experimental study of unsteady gas flow in a dynamic vacuum standard

A dynamic vacuum standard was developed at the Physikalisch-Technische Bundesanstalt (PTB) to test the response of pressure gauges to changes of pressure from 100 kPa to 100 Pa within one second. It has been validated through a series of comparisons of the pressure and temperature evolution curves between simulations and measurements. On the theoretical side, hybrid continuum-particle and conjugate heat transfer simulations were employed, as well as significant modelling based on the choked flow hypothesis. On the measurement side, fast responding capacitance diaphragm gauges (CDGs) and a micrometre sized thermocouple were used to obtain the experimental data. Three conductance elements and various gases have been considered. The comparisons between simulations and measurements show reasonable agreement, with an average deviation of 13.5% in pressure and 9 K in temperature.