Computation of the effective area and associated uncertainties of non-rotating piston gauges FPG and FRS

Abstract

The effective areas of three force-balanced piston gauges (FPGs) and two Furness Rosenberg standards (FRS) in the operating pressure range of each device varying for 1 Pa-15 kPa have been accurately computed both in the gauge and absolute modes. Geometrical data for the non-rotating piston-cylinder assemblies (PCAs) have been provided by the National Metrology Institutes (NMIs) of PTB, RISE, INRiM and CMI. Since the flow is in a wide range of the Knudsen number, simulations have been based on the Batnagar-Gross-Krook (BGK) kinetic model equation, while the typical Dadson and CFD approaches have been complimentary applied only in the viscous regime. Furthermore, an uncertainty analysis has been performed. The effective area is strongly affected by the PCA geometry and the flow conditions, while its dependency on pressure may be different even for devices of the same type. The main source of uncertainty is the dimensional measurements of the piston and the cylinder, followed by the accommodation coefficient characterizing the gas-surface interaction, while the effect of other flow and modeling parameters is negligible. The total relative standard uncertainty of the effective area has been always found to be less than 1 • 10 −5 indicating that pressure measurements of high accuracy can be ensured. Since the effective area is estimated based solely on computations the FPG and the FRS assemblies may be characterized as primary pressure standards.

2D flow model for calculating effective area of piston-cylinder units

“…The absolute pressure of the lubrication gas has a constant value of 140 kPa in gauge mode and 40 kPa in absolute mode. In [10] and [11], the FPG was characterised as a primary pressure standard using PCU's dimensional properties. In that analyses, the 1D flow model was applied with the pressure distribution calculated using RGD methods.…”

“…The high ans indicates a possibility for an uncertainty improvement by its eliminating. Handling the PCU as axisymmetric, ( )  1.3110 -6 was obtained in [11] where uncertainty contributions of the PCU diameters and the RGD model were considered.…”

Gaseous transport phenomena in rarefied conditions via deterministic and stochastic methods with applications in vacuum and fusion engineering

“…These systems are found in several technological fields and applications, including electrical engineering and semiconductor technologies, medicine and medical engineering, physical and chemical vapor deposition processes, drying and degassing processes, vacuum metallurgy and food packaging [3]. In addition, rarefied gas flows play an integral part in the calibration process of industrial pressure gauges, and secondary pressure standards in the intermediate pressure range, which is usually performed by forcebalanced pressure gauges [4,5]. Moreover, vacuum pumping is a critical aspect of many of the aforementioned applications, and huge effort has been made to model various vacuum pumps [6][7][8].…”

“…Large gas pumping systems operating in a wide range of the Knudsen number play a significant role in particle accelerators [9] and fusion reactors [10,11]. In addition, vacuum gas distribution systems may be found in many industrial processes and technological fields including semiconductor technologies, material deposition, vacuum metallurgy, food packaging and metrology [3][4][5]. Since these systems operate from very low pressures (∼ 10 −10 Pa) up to atmospheric pressure, the gas flow may be from the free-molecular regime up to the transition or even the slip and viscous flow regimes.…”

Advanced deterministic and stochastic kinetic modeling of gaseous microscale transport phenomena

“…Vacuum pumps and pumping is one the major technological fields, where kinetic theory and modeling is implemented [9]- [11]. Also, the design and uncertainty analysis performed in pressure sensors and flow meters [12] used in metrology devices and standards [13] are based on measurements supplemented by accurate kinetic simulations. Furthermore, rarefied gas flows appear in semiconductors, filtering, porous media, vapor and chemical deposition processes, etc.…”