A Fundamental Equation of State for Chloroethene for Temperatures from the Triple Point to 430 K and Pressures to 100 MPa

A fundamental equation of state in terms of the Helmholtz energy is presented for chloroethene (vinyl chloride). Due to its fundamental nature, it can be used to consistently calculate all thermodynamic state properties in the fluid region. Based on the underlying experimental database, it is valid from the triple-point temperature 119.31 K to 430 K with a maximum pressure of 100 MPa. In addition to the accurate reproduction of experimental data, correct extrapolation behavior during the development of the equation was attained. This enables the equation to be applied in modern mixture frameworks.

Equation of state to predict the solid-liquid-vapor phase coexistances of pure substances.

A non-cubic equation of state is used to predict the solid-liquid, solid-vapor and liquid-vapor coexistences of pure substances. The equation of state is obtained using as input data the critical point, the boiling temperature, the triple point temperature and the acentric factor of the substance. In this work, some examples of phase diagrams predicted with the equation of state are reported in order to show its capabilities. Finally, a database with the parameters for different pure substances is presented.

Simulation and Real-World Investigation of the Vacuum Pumping Process for Liquid Nitrogen Vapour

We performed the required theoretical computations to simulate the process of pumping saturated liquid nitrogen vapours, accounting for the assumptions adopted. The paper provides a schematic of the test bench and describes the sequence of experiment stages. We checked whether the storage Dewar and volumetric vacuum pump were selected correctly so as to ensure the required evacuation level above the liquid nitrogen surface. We built our test bench and conducted an experiment involving thermostatting in the 63 to 77 K temperature range, and achieved a phase transition in the nitrogen, it turning from liquid to solid. We computed the mass of the nitrogen evaporated required to reach its triple point temperature. We calculated the effective evacuation rate in the system, taking into account the conductivity of separate components. We determined the minimum vapour evacuation time required. We plotted system temperature and pressure as functions of time. The paper describes possible modernisation of the experimental installation, that is, introducing additional crystallisation centres and monitoring the liquid nitrogen mass using electronic scales

Stability of Supersonic Boundary Layer on the Sublimation Surface

Theoretical investigation of the supersonic flat-plate boundary-layer properties under conditions of the surface material sublimation has been performed for Mach number M = 2. Naphthalene (C10H8) was chosen as the substance for the sublimation coating. Performed computations show that with increasing surface temperature due to stagnation temperature increase, the mass flow rate of naphthalene evaporation increases. Calculations performed on the basis of linear stability theory show that such an increase of evaporation leads to a noticeable decrease of the local growth rates of unstable perturbations in the boundary layer. It is found that stabilization of the boundary layer by the surface coating sublimation occurs with increasing temperature of the sublimation coating, reaching a maximum near the triple point temperature of the sublimation material. The carried out experiments confirmed the stabilizing effect of surface sublimation.

An inter-comparison of isotopic composition of neon via chemical assays and thermal analyses (IUPAC Technical Report)

In 2003–2014, a study on the effect of isotopic composition on the triple point temperature of neon was conducted under the framework of a Project involving laboratories from 11 countries. Natural neon from commercial sources of different isotopic composition, high-purity 20Ne and 22Ne isotopes, and certified artificial isotopic mixtures were used. The thermometric studies comprised: a) a total of 131 analytical assays from 3 laboratories on the isotopic composition of samples taken from 31 different bottles of neon with chemical gas purity 99.99 mol % to 99.9995+ mol %, including chemical impurities for some samples, with up to 12 assays per sample; b) multi-laboratory thermal analyses, with accuracies ranging up to better than 50 μK (k≈2), on 39 samples, almost all permanently sealed in metal cells, for the determination of the liquidus-point temperature of the triple point as a function of isotopic composition. The thermometric studies also constitute an international inter-comparison of thermal and analytical assays on the isotopic composition—and occasionally of the chemical impurities—of neon. These tests are critically needed for top-accuracy thermometry. The main results of the inter-comparison of the various chemical assays, and of the comparisons between the assays and the results of thermal analyses, are reported. They show discrepancies in x(20,21,22Ne), especially for x(22Ne), in ‘natural’ neon, for the same gas bottle, equivalent to an uncertainty of up to 165 μK (k = 1) in the triple point temperature, as measured by all testing laboratories, and of about 100 μK (k = 1) as measured from a single testing laboratory. This is an unsatisfactory situation for thermometry, since it is difficult to obtain a reliable and accurate isotopic assay for neon, thus limiting the accuracy of the realisation of the neon triple point temperature as a ITS-90 reference point to well above 50 μK. However, it also discloses a strong limitation in the relevant analytical chemistry.