Wire-mesh Sensors: Recent Developments and Applications

Wire-mesh sensors (WMS) are today well established measurement tools to obtain both temporally and spatially highly resolved structural information as well as averaged phase fraction and phase fraction distribution data in air-water and steam-water two-phase flow experiments. Those data, with a spatial resolution of down to 0.5 mm and frame rates up to 10,000 frames per second are suitable to validate CFD code developments. During the last decade, the technology has widely spread in research laboratories all over the world and has been more and more developed towards a turnkey machine for researchers. In this work we summarize the most recent developments in hardware for high temperature and high pressure applications, new electronics with integrated void fraction calculations and flow pattern identification for industrial applications and latest software developments for data analysis and visualization.

A big issue for the application of wire-mesh sensor technology to high pressure high temperature facilities is the complicated pressure-proven and temperature-resistant insulated support and feedthrough of the measuring electrodes. Our new development facilitates a compact metallic body with flanges on both sides with a slot in sensor unit consisting of ceramic insulators and a stainless steel frame. The feedthrough of the wires is realized by commercially available multiple feedthrough fittings.

The most common and proved codes for WMS data analysis have been capsulated in our wire-mesh sensor data processing FrameWork. The tool has got a new, user friendly graphical interface and allows the implementation of new algorithms by the end user. The resulting data and profiles can be visualized within the software and a batch processing tool allows automated “over the weekend” jobs.

The wire-mesh sensor technology so far is a scientific tool for researchers. The huge amount of data, several gigabytes for one measurement of a couple of seconds, has to be stored and processed offline later on. For industrial applications, the users need online data on liquid/gas holdups and flow pattern in the pipelines. An industrial type of wire-mesh sensor electronics has been developed based on an FPGA (field programmable gate array) microcontroller calculating the frame averaged void fraction instantaneously and moreover identifying the flow pattern based on statistical values of the last 10 seconds from the two-phase flow using Fuzzy clustering algorithm.