Calibration of laminar flow meters for process gases

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• 作者：John D. Wright^a ; ^{john.wright@nist.gov} ; Thiago Cobu^b ; ¹ ; ^{thiagoc@ipt.br} ; Robert F. Berg^a ; ^{rberg@nist.gov} ; Michael R. Moldover^a ; ^{Michael.moldover@nist.gov}
• 关键词：Laminar flow meter ; Calibration ; Gas species ; Gas properties ; Rate of rise ; Dynamic flow standard ; Gravimetric flow standard ; Process gases
• 刊名：Flow Measurement and Instrumentation
• 出版年：2012
• 期刊代码：65_09555986
• 类别：et
• 出版时间：June, 2012
• 卷：25
• 期：Complete
• 页码：8-14
• 文件大小：960 K

摘要

We calibrated three models of commercially-manufactured, laminar flow meters (LFMs) at four pressures (100, 200, 300, and 400 kPa) with five gases (N₂, Ar, He, CO₂, and SF₆) over a 10:1 flow range using NIST鈥檚 primary flow standards as references. We combined three items: (1) the calibration data acquired with N₂, (2) gas-property data from NIST鈥檚 database REFPROP 9.0, and (3) a physical model for each LFM that accounts for the effects of viscosity, entrance and exit effects, gas expansion, gas non-ideality, and slip. This combination predicted the calibrations for the flow of Ar, He, CO₂, and SF₆ with a maximum error of 0.8%for Reynolds numbers . Under these conditions, the present LFM model allows prediction of calibration results for other gases with approximately three times more accuracy than conventional approaches that plot the flow coefficient as a function of the viscosity coefficient or Re. We represented the calibration data for SF₆ in the range 500 by adding an empirical quadratic function to the model for one of the LFMs.