Comparative study of aerodynamic behaviour of three flow conditioners

Accuracy and precision of flow meters are the most important metrological parameters in most industries dealing with increasingly expensive fluids. The accuracy of these devices depends not only on their construction and method of operation but also of their position in the pipe network. Pipe fittings such valve, bends and other fixtures generate turbulence and swirl and distort the flow distribution in the pipe. The present paper is concerned with an experimental study of the decay process of highly swirling flow in a circular pipe and its effect on orifice flow meter reading. The efficiency of three flow conditioners (The Etoile and the Tube bundle straighteners described in the Standards ISO 5167 and the Laws perforated plate) to remove swirl and to reduce metering errors has been investigated using a two components Laser Doppler Anemometer. Highly swirling flow distortion was generated by a 90° out of planes double bend upstream the flow meter. Discharge coefficient shifts due to the flow distortion was determined for three orifice meters with a diameter ratio □=0.5, 0.62 and 0.70 at flow Reynolds number ranging from 0.79 to 3.21x10 5 . The results show that the disturbance causes important deviations in the meter's calibration coefficient. The effectiveness of the flow conditioning devices to remove the flow distortion and to reduce the resulting metering error was not evident for all the working conditions studied here.