High Level Humidity Generator for Nitrogen-Water Mixtures

Abstract:A high level humidity generator has been developed at the National Institute of Standards and Technology (NIST). This device provides the capability for research, testing and calibration at high levels of water vapor content in such gases as hydrogen, nitrogen, and ambient air for applications such as hydrogen-powered fuel cells, standard reference materials and food processing. The generator produces a gas stream of nitrogen-water vapor mixture having mixing ratios from 0.16 g to 1.47 g of water vapor per gram of dry nitrogen (g H2O/g dry N2). This is equivalent to dew point temperatures of 60 °C to 90 °C at standard atmospheric pressure and to water vapor pressures of 19 948 Pa to 70 182 Pa. The generated gas can be fed to a test chamber with independent temperature control from 25 °C to 200 °C and pressure control from 0.1 MPa to 1.5 MPa, for the calibration of hygrometers. Inter-comparisons with a NIST reference standard dew point hygrometer gave results that in all cases agreed to within 0.0...