Generator of variable gas flows using an isothermal chamber

There is no effective method to calibrate the dynamic characteristics of gaseous flow meters. This is because the density of these fluids changes largely with respect to the variation in both pressure and temperature. The present paper describes the development of an unsteady mass flow generator for gases. The generator consists of an isothermal chamber and two spool-type servo valves. The heat transfer area within the isothermal chamber is made sufficiently large by stuffing the copper wool materials to ensure that the essential isothermal conditions are preserved. The calibration of the dynamic characteristics of the gaseous flow meters and the internal flows within such meters are achieved using the generator. Experimental tests reveal that the generator can control oscillatory flows at a frequency of up to 50 Hz with an uncertainty of 5.5%. In addition, the unsteady mass flow generator can generate flows for more than 30 min. Thus, the effectiveness of the generator is demonstrated.