On the accuracy of wire-mesh sensors in dependence of bubble sizes and liquid flow rates

Abstract

An experimental study to assess the accuracy of wire-mesh sensors in dependence of bubble sizes and flow rates has been performed in a 50mm×50mm transparent rectangular channel. The liquid superficial velocities were ranging from 0m/s up to 0.62m/s with the obtained bubble size ranging from 3mm to 7mm. A single wire-mesh sensor with 16×16 electrode wires was used with a temporal and spatial resolution of 10kHz and 3.1mm (lateral distance between two wires), respectively. Single bubbles with known bubble size, subsequently called reference bubble size, was injected into the test section via bubble injector approx. 25cm upstream of the wire-mesh sensor. The bubble size measurement by using wire-mesh sensor cannot be obtained directly since it requires the information of bubble velocity which is not available only by installing a single sensor. Therefore, a stereoscopic observation was conducted to obtain the bubble velocity by tracking the successive frames as well as to study the intrusiveness of the sensor. This configuration gave an advantage that the registered bubble will be assigned with its real approach velocity and a better agreement is expected. As the result, a direct comparison of all individual bubbles with the reference bubble size showed an agreement within ±10%. However, a deceleration effect was found for low superficial and observed to disappear as the liquid superficial velocity increased then vanish at observed JL=0.62m/s.