Flowmeter calibration facility for heated gas mixtures

The National Institute of Standards and Technology (NIST) has designed and built a new gas calibration facility that permits flowmeter performance testing under conditions of variable flow, temperature, and gas composition. The facility meters pure air, nitrogen, carbon dioxide, and argon with critical flow nozzles that have been calibrated using existing NIST gas flow standards. Water vapor is added in a saturator vessel and the mass flow of water is calculated from a dew point temperature measurement. The metered gas mixture is heated by an electric circulation heater to temperatures between 293 and 700 K. The flow range of the facility is nominally 60 to 6200 liters per minute and the uncertainty of the flow is 1% of reading or less. Testing of flowmeters is underway with temperature and composition conditions which simulate automobile exhaust.