Development of simultaneous measurement system for instantaneous density, viscosity and flow rate of gases

In the present paper, we presented a novel simultaneous measurement system for the density and viscosity of gases. The principle of the proposed system is the combination of two flow sensors that use different measurement principles. The combined sensor consists of an isothermal chamber, a micro hot wire anemometer, a diaphragm type differential pressure sensor and a bi-cylindrical flow channel. The volumetric flow rate can be obtained from the pressure change of gas in an isothermal chamber. The density can then be obtained from the flow rate and the mass flow rate measured with a micro hot wire anemometer. At the same time, the viscosity can be obtained from the volumetric flow rate and the pressure difference at the flow channel. The micro hot wire anemometer used in the present system is fabricated by micromachining technology. The effectiveness of the simultaneous measurement system is confirmed through experiments using air and carbon dioxide.