A novel gas divider using nonlinear laminar flow

• Published in: Flow measurement and instrumentation 2016-12, Vol.52, p.255-260
• Main Authors: Nuszkowski, J., Schwamb, J., Esposito, J.
• Format: Article
• Language: English
• Subjects: Capillary tube; Compressible fluid; Flow measurement; Gas dilution; Gas divider; Laminar flow
• ISSN: 0955-5986; 1873-6998
• DOI: 10.1016/j.flowmeasinst.2016.10.016

Gas dividers are important in emissions measurement since they continuously and accurately mix two gases to create a known gas concentration that is needed in the multi-point calibration of gas analyzers. A novel gas divider was designed using nonlinear laminar flow induced from the density change along the capillary channels due to the high-pressure drop (relative to the inlet gas pressure). The minor losses from entrance and exit effects can be ignored due to the high pressure loss from Hagen-Poiseuille's law relative to the minor losses. Small diameter wires inside of a tube were used to create capillary channels through which gas could flow. The gas divider, using nonlinear laminar flow, showed lower measurement uncertainty at high (90%) dilution levels than using linear laminar flow due to the higher-pressure drop at the same volumetric flow rates. Experiments showed the expected gas concentration from using the gas divider to be within 2% of the measured gas concentrations. •A gas divider was developed based on nonlinear laminar flow.•Formulas describing the relationship between pressure drop and volumetric flow were developed that included corrections for viscosity, outlet pressure, and minor losses.•The formulas and the gas divider were verified by experiments.