Mass flow-based air permeability standard measurement method

To avoid the influences of environmental factors on the air permeability standard measurement and the variation of pressure drop across the standard in volume flow method, a method based on mass flow was established. The method combines the mass flow element with a controller to obtain the mass flow through the standard and converts the mass flow into the volume flow by calculation. A control system was developed on the basis of LabVIEW software to regulate the pressure drop across the standard and keep it within the set range. The repeatability and stability of the established method were tested with air permeability standards of different specifications, and the data were compared with those of volume flow method and international collaborative experiments. The results showed that: 1) The coefficients of variation of the measurement results of mass flow method and volume flow method distributed around 0.2%, and their relative extreme difference around 1%. The two methods had similar repeatability and stability. 2) The coefficients of variation of the measurement results of mass flow method and international collaborative experiments distributed around 0.2%, their relative deviation distributed around 1% and their maximum relative deviation was 1.91%. The two showed pretty good agreement. The established mass flow method can measure air permeability standard stably and accurately, it provides a support for improving the automation of measurement devices.