Response of electrical film thickness sensors to waves in the liquid film

Horst-Michael Prasser

doi:10.1016/j.nucengdes.2021.111304

Abstract

The electrical liquid film thickness (LFT) sensor developed at ETH Zurich is applied to study wavy annular flows. The LFT sensor consists of a matrix of electrodes put flush to the surface of the wall at which the liquid film of interest is present. The conductance between transmitter and receiver electrodes is sampled and converted into a film thickness using a calibration function obtained for a flat liquid film without waves. Due to limited lateral resolution and non-linear sensor response, waves are characterized with measuring errors, which depend on the wave height, length and angle of attack. The paper presents the result of potential field simulations of waves passing over the sensor surface. The wave parameters obtained from the simulated sensor signals are compared to the input. The results are used to quantify the uncertainty of dynamic film thickness measurements. The obtained detailed information on the sensor response allows a better interpretation of experimental results.

Highlights

Electrical conductance based liquid film sensors that are capable in field measurements were first presented by Belt et al (2007), Belt et al (2010), Da Silva et al (2008), Damsohn (2011), Damsohn and Prasser (2009) and Damsohn and Prasser (2009a)
Potential field simulations of idealized waves running over the sur face of our electrical film thickness sensor were carried out
Single waves are displayed as an object with two peaks of liquid film thickness instead of one

Summary

Introduction

Electrical conductance based liquid film sensors that are capable in field measurements were first presented by Belt et al (2007), Belt et al (2010), Da Silva et al (2008), Damsohn (2011), Damsohn and Prasser (2009) and Damsohn and Prasser (2009a). The LFT sensor consists of a matrix of electrodes put flush to the surface of the wall at which the liquid film of interest is present. In all three mentioned cases, the information is read-out by the signal acquisition method developed for wire-mesh sensors. Such a sensor has a non-linear char acteristic. The locally measured conductance is a non-linear function of the LFT. For the conversion of the primary signals into LFT values, the characteristic has to be known and applied as a calibration function

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Results

Conclusion