Use of sonic anemometry for the study of confined swirling flows in large industrial units

This work explores the methodology and errors involved in using a commercial sonic anemometer to study confined industrial swirling air flows, such as those in large cyclones or dryers in the order of hundreds of m3. Common sources of uncertainty in time-of-flight techniques and multiple-path anemometry are evaluated and corrections and methodology guidelines are proposed to deal with issues typical of full scale measurement. In particular, this paper focuses on quantifying the error associated with the disruption of the local flow caused by a HS−50 horizontal sonic anemometer under a range of turbulence characteristic of industrial swirl towers. Under the guidelines proposed and the conditions studied here, the presence of the instrument originates a measurement error <1−4% in velocity, <1−3° in direction and <7−31% in turbulent kinetic energy for an isothermal flow in the absence of solids. These ranges are above traditional uses of sonic anemometry in meteorology due to the limitations inherent to industrial units, but remain within reasonable margins for engineering applications. Laser diagnostic methods are widely used in laboratory and pilot scale cyclones or dryers but are rarely applicable to large production scales. In this context, the data collected with sonic anemometers render much lower resolution but appear in agreement with historical Particle Image Velocimetry. Methods such as the one proposed here can be a useful alternative to improve the level of detail of fluid dynamic studies in industrial units, which are often qualitative or with a limited validation.