High-speed liquid film sensor with high spatial resolution

Abstract

A novel sensor based on the electrical conductance method is presented to measure the thickness of the dynamic liquid films in two-phase flow. Two sensors with different properties have been developed consisting of a matrix with 64 × 16 measuring points and a time resolution of 10 000 frames s−1. The electrode geometries of the sensors are optimized by potential field calculations. The first liquid film sensor (LFS 1) has its electrodes arranged in lines and measures film thickness up to 800 µm with a square spatial resolution of 3.12 × 3.12 mm2 and a crosstalk below 0.5%. The second sensor (LFS 2) has its electrodes arranged in rhombuses and measures liquid films between 100 and 700 µm with a square spatial resolution of 2 × 2 mm2 and a crosstalk below 3%. The sensors are produced with a standard PCB etching technology. The calibration experiments show that the liquid film sensor delivers reproducible results with a standard deviation below 2% of the end value. Comparing two different calibration methods, it becomes obvious that the film thickness is also measured correctly when sloped film surfaces are present. The sensors are tested in horizontal and vertical co-current air–water flow experiments. The experiments show that the sensors are capable of resolving wave patterns and local droplet deposition in annular flow.