Abstract
A novel mass flow meter based on ultrasound technology
By Dr. Jerker Delsing
Dept. of Heat and Power Engineering Lund Institute of Technology, Sweden
A novel technique for mass flow measurement of liquids is presented. The technique is based upon use of ultrasound for the measurement of flow velocity and
fluid density.
The flow velocity is measured by mean of transit time or sing-around technique.
Here we used the sing-around technique. The flow meter developed at Heat and Power Engineering show accuracy's of better then ± 1% with repeatability of better than 0.1%. This is obtained within a dynamic flow range of 1:40.
The density is determined using an ultrasonic reflection technique for acoustic impedance measurement of a fluid. The acoustic impedance Z=c*r where c is the fluid speed of sound and r is the fluid density. Provided that we can measure both the speed of sound and the acoustic impedance we have a measurement of the fluid density. The technique applied for acoustic impedance measurement is a reflection technique where the influences from temperature effects are compensated for.
Preliminary density measurements show accuracy's of better than ±0.6%. Further the influence from dust deposition of the density probe was investigated showing that deposition layer of less than 20m m does not affect the density measurement.
By combining these two techniques it is possible to obtain a mass flow meter for liquids using only two ultrasound transducers. Possible accuracy's of such a device is better than ±1-2%. This accuracy's can possible be obtained to costs that is marginal compared to the costs of Coriolis type mass flow meter of today.
