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Publication Citation: Calibration of Laminar Flow Meters for Process Gases

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Author(s): John D. Wright; Thiago Cobu; Robert F. Berg; Michael R. Moldover;
Title: Calibration of Laminar Flow Meters for Process Gases
Published: June 01, 2012
Abstract: We calibrated three models of commercially-manufactured, laminar flow meters (LFMs) at four pressures (100 kPa, 200 kPa, 300 kPa, and 400 kPa) with five gases (N2, Ar, He, CO2, and SF6) over a 10:1 flow range using NIST‰s primary flow standards as references. We combined three items: (1) the calibration data acquired with N2, (2) gas-property data from NIST‰s 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 Re < 500. Under these conditions, the present LFM model is approximately 3 times more accurate than conventional calibrations 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 < Re < 2000 by adding an empirical quadratic function to the model for one of the LFMs.
Citation: Flow Measurement and Instrumentation
Keywords: laminar flow meter; calibration; gas species; gas properties; rate of rise; dynamic flow standard; gravimetric flow standard; process gases
Research Areas: Measurement Standards, Flow, Calibrations, Standards, Manufacturing, Metrology
PDF version: PDF Document Click here to retrieve PDF version of paper (592KB)