Applicable Pressure Range Research Articles

Toward an international practical pressure scale: A proposal for an IPPS ruby gauge (IPPS-Ruby2020)

ABSTRACT At the 26th AIRAPT conference in 2017, a task group was formed to work on an International Practical Pressure Scale (IPPS). This report summarizes the activities of the task group toward an IPPS ruby gauge. We have selected three different approaches to establishing the relation between pressure (P) and ruby R1-line shift (Δλ) with three groups of optimal reference materials for applying these approaches. Using a polynomial form of the second order, the recommended ruby gauge (referred as Ruby2020) is expressed by: , where λ0 is the wavelength of the R1-line near 694.25 nm at ambient condition. In June of 2020, the Executive Committee of AIRAPT endorsed the proposed Ruby2020. We encourage high-pressure practitioners to utilize Ruby2020 within its applicable pressure range (up to 150 GPa), so that pressure data can be directly compared across laboratories and amended consistently as better scales emerge in the future.

A modified equation of state for Xe at high pressures by molecular dynamics simulation

The exact equation of state (EOS) for the fission gas Xe is necessary for the accurate prediction of the fission gas behavior in uranium dioxide nuclear fuel. However, the comparison with the experimental data indicates that the applicable pressure ranges of existing EOS for Xe published in the literature cannot cover the overpressure of the rim fission gas bubble at the typical UO2 fuel pellet rim structure. Based on the interatomic potential of Xe, the pressure—volume—temperature data are calculated by the molecular dynamics (MD) simulation. The results indicate that the data of MD simulation with Ross and McMahan's potential [M. Ross and A. K. McMahan 1980 Phys. Rev. B 21 1658] are in good agreement with the experimental data. A preferable EOS for Xe is proposed based on the MD simulation. The comparison with the MD simulation data shows that the proposed EOS can be applied at pressures up to 550 MPa and 3 GPa and temperatures 900 K and 1373 K respectively. The applicable pressure range of this EOS is wider than those of the other existing EOS for Xe published in the literature.

Experimental Research on the Expansibility Factor Calculation Model of V-Cone Flowmeters

This article aims to improve the accuracy of gas flow measurement of cone flowmeter and get a high-precision expansibility factor calculation model with wide applicable pressure range and different upstream side pressure. The experimental research was based on the DN50 and DN100 two sets of V-Cone flowmeter designed by Tianjin University. As the standard gas flow facility by means of critical flow venturi nozzles was insufficient supply capacity and poor pressure stability in positive pressure method, the experimental data obtained from standard gas flow facility by using negative pressure method was used to fit out the V-Cone flowmeter expansibility factor calculation model --TJU-2012 model. The model was tested with the experimental data obtained from the standard gas flow facility and compared with other four cone flowmeter expansibility factor calculation models, its maximum relative error was better than 0.9% and square averaged root error was better than 0.6%, both of them are the least.

EuCl2 Powder as a Pressure-Memory Material

By utilizing the effect of an unusually large residual stress on the photoluminescence spectra of EuCl2 powder, we found that the EuCl2 powder appears to have potential as a pressure-sensor material for cases where in situ pressure measurements are difficult. The applicable pressure range is roughly 0–1.3 GPa. The photoluminescence peak position of the EuCl2 powder is significantly redshifted after the EuCl2 powder has experienced pressure; in other words, the maximum pressure the powder has experienced is reflected in the luminescence peak shift of the recovered powder. Some technical points for using the EuCl2 powder as a pressure-sensor material are also discussed.

Saturated-Steam Pressure Drop in Flow Through Porous Media

Summary This note provides a simple steady-state method for estimating the pressure drop for steam vapor flowing at a constant mass rate through porous media. The derived formula includes the relevant properties of saturated steam and allows for their distribution along the zone of pressure variation. It also eliminates the need for steam tables within the applicable pressure range (10-2,900 psia). The method can also be extended to cases in which the rate varies in a known manner because of heat loss or other factors.

Thermal contact resistance at low contact pressure: Effect of elastic deformation

Existing models over-predict the thermal contact resistance of conforming rough joints at low contact pressures. However, the applicable pressure range in some applications such as microelectronics cooling is low. A new model is developed which is more suitable for low pressures. The effect of elastic deformations beneath the plastically deformed microcontacts is determined by superimposing normal deformations due to self and neighboring contact spots in an elastic half-space. A parametric study reveals that the elastic deformation effect is an important phenomenon at low contact pressures. The model is compared with data and good agreement is observed at low contact pressures.

Tritium concentration measurements in the Joint European Torus divertor by optical spectroscopy of a Penning discharge

Obtaining precision measurements of the relative concentrations of hydrogen, deuterium, tritium, and helium in the divertor of a tokamak is an important task for nuclear fusion research. Control of the deuterium–tritium isotopic ratio while limiting the helium ash content in a fusion plasma are key factors for optimizing the fuel burn in a fusion reactor, like the International Tokamak Experimental Reactor. A diagnostic technique has been developed to measure the deuterium–tritium isotopic ratio in the divertor of the Joint European Torus with a species-selective Penning vacuum gauge. The Penning discharge provides a source of electrons to excite the neutral hydrogen isotopes in the pumping duct. Subsequently, the visible light from the hydrogen isotopes is collected in an optical fiber bundle, transferred away from the tokamak into a low radiation background area, and analyzed in a high resolution Czerny–Turner spectrometer, which is equipped with a fast charge coupled device camera for optical detection. The intensity of the observed line emission (Dα−6561.03 Å and Tα−6560.44 Å) is directly proportional to the partial pressure of each gas found in the divertor. The line intensity of each isotope is calibrated as a function of pressure. The ratio of the line intensities thus provides a direct measurement of the deuterium–tritium isotopic ratio. The lower limit for the determination of the deuterium–tritium isotopic ratio is about 0.5%. The applicable pressure range for this system is from 10−5 to a few times 10−3 mbar.

Unified formulation of isothermal adsorbate flow in mesoporous media over the full vapor pressure range

Surface flow plays an important role in phenomena of gas or vapor transport in mesoporous pellets or membranes, which are of considerable practical interest; but a satisfactory unified formulation of surface flow over the whole applicable pressure range is as yet lacking. In analogy with gas phase flow (which varies from diffusive at low, to viscous at high, pressures), surface transport varies from diffusive, in the dilute monolayer region, to hydrodynamic, when the adsorbate is in the form of multimolecular layers or liquid condensate. Transport in these cases has been formulated in terms of a Fick surface diffusion coefficient or a hydrodynamic surface permeability respectively. We demonstrate here that attempts which have been made to extend each one of these formulations into the region of the other do not lead to physically acceptable results. We further show that an irreversible thermodynamic approach leads to the desired unified formulation of a “thermodynamic” diffusion coefficient, which appears to vary smoothly between the Fick value at infinite dilution and the value derived from the liquid permeability of the porous medium.

Single-pulse photoacoustic technique for measuring IR multiphoton absorption by polyatomic molecules

The single-pulse photoacoustic technique was used to measure cross sections for IR multiphoton absorption. A discussion of this technique and the applicable pressure range is given. The source of the signals from the microphone was identified. The first peak is proportional to the energy absorbed by the gas in the focal region, while the subsequently arriving signals correspond to a mixture of the signal from the entrance and exit volumes and the ringings of the microphone and the gas cell.