The gas flowmeter here reported is a movable L tube flowmeter of angular momentum type with a thermometer and a manometer.
Such a flowmeter enables us to know the mass flow rate of a gaseous substance by measuring the torque on the movable L tube, the temperature and pressure at the inlet (or outlet) end of the tube.
The theory of the flowmeter assumes the uniformity of velocity at the inlet (or outlet) end. When this assumption is invalid, the discharge coefficient becomes necessarily to correct the error. The experimental results show that the discharge coefficient for gas is equal to that for liquid, and the latter can be known experimentally with liquid.