Errors in Rate of Rise Gas Flow Measurements from Flow Work

Published: March 21, 2018


John D. Wright, Aaron N. Johnson, Gina M. Kline, Michael R. Moldover


The rate of rise (RoR) method measures the time rate of change of the mass of gas in a collection volume as it is filled via a flow meter under test. The mass of gas is calculated from time-stamped pressure and temperature data gathered from the known collection volume as it is filled. Making accurate RoR measurements requires reliable gas pressure and temperature values as the collection tank is filling with gas. We present a thermodynamic model and experimental measurements of gas temperature errors that are a function of the dimensionless ratio: {heat transfer from the gas to its surroundings} / {the energy input to the gas by flow work}. The uncertainty of RoR flow measurements made using the NIST 34 L collection tank are < 0.12 % for flows between 1 sccm and 200 sccm, but at lower flows and higher flows, RoR uncertainty rises to approximately 1 % due to leaks and flow work induced temperature errors.
Conference Dates: March 21-23, 2018
Conference Location: Queretaro, -1
Conference Title: International Symposium for Fluid Flow Measurement
Pub Type: Conferences

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gas flow, rate of rise, primary standard, uncertainty
Created March 21, 2018, Updated July 26, 2018