Validation of a PTB force-balanced piston gauge primary pressure standard

Experimental methods using different pressure standards were applied to verify theoretical results obtained for the effective area of the piston-cylinder assembly (PCA) and for pressures measured with a force-balanced piston gauge (FPG). The theoretical effective area was based on the PCA’s dimensional properties defined via diameter, straightness and roundness measurements of the piston and cylinder, derived by gas-flow modelling using principles of the rarefied gas dynamics, and presented as two values: one obtained for absolute and the other for gauge pressure operation mode. Both values have a relative standard uncertainty of 5×10<sup>-6</sup>. The experimental methods chosen were designed to cover the entire operating pressure range of the FPG from 3 Pa to 15 kPa. Comparisons of the FPG with three different PTB pressure standards operated in different pressure ranges – a pressure balance, a mercury manometer and a static expansion system – were performed using the cross-float method and by a direct comparison of the generated pressures. For the theoretical and experimental effective area, as well as for pressures generated by the FPG and the reference standards, all the results demonstrated full agreement within the expanded uncertainties of the standards.

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Rarefied gas flow in pressure and vacuum measurements

ACTA IMEKO ◽

10.21014/acta_imeko.v3i2.101 ◽

2014 ◽

Vol 3 (2) ◽

pp. 60 ◽

Cited By ~ 6

Author(s):

Jeerasak Pitakarnnop

Keyword(s):

Gas Flow ◽

Rarefied Gas ◽

Slip Flow ◽

Effective Area ◽

Low Flow ◽

Vacuum System ◽

Rarefied Gas Flow ◽

Pressure Balance ◽

Piston Cylinder ◽

Flow Leak

Flows of a gas through the piston-cylinder gap of a gas-operated pressure balance and in a general vacuum system have one aspect in common, namely that the gas is rarefied due, respectively, to the small dimensions and the low pressure. The flows in both systems could be characterised as being in either slip-flow or transition regimes. Therefore, fundamental research of flow in these regimes is useful for both pressure and vacuum metrology, especially for the gas-operated pressure balance where a continuum viscous flow model is widely used for determining the effective area of the pressure balance. The consideration of gas flow using the most suitable assumption would improve the accuracy of such a calculation. Moreover, knowledge about rarefied gas flow will enable gas behaviour in vacuum and low-flow leak detection systems to be predicted. This paper provides useful information about rarefied gas flow in both slip-flow and transition regimes.

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Verification of Gas Flow Traceability from 0.1 sccm to 1 sccm Using a Piston Gauge

NCSLI Measure ◽

10.51843/measure.13.3.4 ◽

2021 ◽

Vol 13 (3) ◽

pp. 10-16

Author(s):

Michael Bair

Keyword(s):

Laminar Flow ◽

Gas Flow ◽

Vertical Displacement ◽

Pressure Control ◽

Effective Area ◽

Flow Measurements ◽

Piston Cylinder ◽

Measurement Assurance ◽

Piston Gauge ◽

Means Of Measurement

Fluke Calibration is accredited for gas flow measurements in the range of 0.1 sccm to 6000 slm in nitrogen and air. Traceability is maintained directly through a gravimetric f low standard but only recently from 1 sccm to 10 sccm. The traceability of flow in the range of 0.1 sccm to 1 sccm is based on extrapolation of the use of laminar flow elements (LFE) below 1 sccm. This part of the range has never been completely verified through interlaboratory comparisons, proficiency testing or other means of measurement assurance. In an internal document from DH Instruments in the early 1990s it was suggested that a piston gauge might improve traceability for very low gas flows. In order to prove out traceability in this range an attempt was made to use a piston gauge using a piston-cylinder size of 35 mm diameter as a reference. One reason for choosing a piston gauge as a reference is its pressure control. This is crucial when measuring gas flow through a LFE in this design and range. In addition, the effective area is known to within 0.001 %, leaving the vertical displacement of the piston to dominate the uncertainty of the dimensional part of the flow test. This was a challenge because the measurements required absolute mode and the internal piston position sensor supplied with the piston gauge did not have sufficient precision. This paper describes the theory and design of the gas flow measurement system, the current results, and improvements desired or suggested. Two different designs are discussed, one with a single piston gauge as a reference and one with two piston gauges measuring flow on either side of the laminar flow element. Note: sccm (standard cubic centimeters per minute) is an industry accepted alternative to kg/s [1]. It is used out of convenience to normalize flow rates of gases with significant differences in density.

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Analysis for Rarefied Gas Flow in a Rotating Cylinder

Volume 1: Symposia, Parts A, B and C ◽

10.1115/fedsm2009-78356 ◽

2009 ◽

Author(s):

H. Futagami ◽

H. Ninokata

Keyword(s):

Gas Flow ◽

Rarefied Gas ◽

Isotope Separation ◽

Direct Simulation Monte Carlo ◽

Rotating Cylinder ◽

Navier Stokes ◽

Operating Pressure ◽

Direct Simulation ◽

Navier Stokes Equation ◽

Simulation Monte Carlo

Behaviors inside rotating cylinders where the range of operating pressure is very wide, i.e. from subatmospheric to almost vacuum are subject of this study. The flow near the rotating axis is very rarefied. If a flow becomes rarefied, the flow cannot be treated as that of a continuum media. Therefore the flow cannot be analyzed by the method based on solving Navier-Stokes equation. One of the promising methods is considered to be DSMC (Direct Simulation Monte Carlo) method based on Boltzmann equation ([1]). In this paper, fundamental validation analyses related to isotope separation in a rotating cylinder calculations of endplate type centrifuge were performed for the parametric study, with DSMC. The results were compared with the experimental results by Groth et al ([2]). The validity of the calculations and its limit were also discussed.

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GAS EXTRACTION FROM AIR INTAKE IN THE TRANSIENT REGIME OF RAREFIED GAS FLOW

TsAGI Science Journal ◽

10.1615/tsagiscij.2018029670 ◽

2018 ◽

Vol 49 (7) ◽

pp. 713-722

Author(s):

Alexander Ivanovich Erofeev

Keyword(s):

Gas Flow ◽

Rarefied Gas ◽

Transient Regime ◽

Gas Extraction ◽

Rarefied Gas Flow ◽

Air Intake

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Simulation of Gas Flow Over a Micro Cylinder

ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer, Volume 1 ◽

10.1115/mnhmt2009-18288 ◽

2009 ◽

Cited By ~ 3

Author(s):

Yuan Hu ◽

Quanhua Sun ◽

Jing Fan

Keyword(s):

Reynolds Number ◽

Mach Number ◽

Drag Coefficient ◽

Gas Flow ◽

Rarefied Gas ◽

Low Reynolds Number ◽

Pressure Drag ◽

Low Reynolds ◽

Rarefied Gas Effect ◽

Gas Effect

Gas flow over a micro cylinder is simulated using both a compressible Navier-Stokes solver and a hybrid continuum/particle approach. The micro cylinder flow has low Reynolds number because of the small length scale and the low speed, which also indicates that the rarefied gas effect exists in the flow. A cylinder having a diameter of 20 microns is simulated under several flow conditions where the Reynolds number ranges from 2 to 50 and the Mach number varies from 0.1 to 0.8. It is found that the low Reynolds number flow can be compressible even when the Mach number is less than 0.3, and the drag coefficient of the cylinder increases when the Reynolds number decreases. The compressible effect will increase the pressure drag coefficient although the friction coefficient remains nearly unchanged. The rarefied gas effect will reduce both the friction and pressure drag coefficients, and the vortex in the flow may be shrunk or even disappear.

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