Performance tests of two insertion type thermal mass flow meters

Thermal mass flow meters are widely used in industry for process and plant mass flow metering for a wide range of gas types. The interest of this type of flow meter lies in the fact that the induced pressure drop is negligible; the wide turndown allows measurement of gas consumption as well as leaks. However, the operating conditions of flow meters are sometimes far from the conditions for which the manufacturer specifications are given and the objective of the performed tests is therefore the evaluation of the measurement error which can occur when the use conditions deviate from the calibration conditions. First, tests in “ideal” conditions (no upstream disturbances, ambient conditions of pressure, temperature and humidity) have been performed to check if the flow meters meet their manufacturer’s specifications. Then, some operating conditions have been changed. The investigated parameters were the gas temperature, the gas humidity, the in-line pressure, the orientation of the sensor relative to the flow direction and the distance to upstream disturbances. Tests have been conducted with upstream distances equal to, smaller and higher than the minimum distance required by the manufacturer. The study presented in this paper has been conducted for two insertion type thermal mass flow meters