Abstract:To study and measure the viscosity coefficient of unknown gas, a simple measuring device based on capillary was built. According to Poiseuille's law, the relationship between gas volume flow and viscosity coefficient was established. With nitrogen(N2) as the calibration standard gas, the viscosity coefficients of hydrogen(H2), carbon dioxide(CO2) and synthetic air in the temperature range of 280~320K and the pressure range of 169kpa~376kpa were calculated by measuring the volume flow. The reliability of this method is theoretically analyzed, and the results are compared with the viscosity coefficient in NIST database. The relative error rate of this method is in the range of [-1.109%, 1.779%] when the differential pressure is in the range of 103~206kPa.