Liquid Film Sensors
Liquid film sensors are based on the signal acquisition technique that was developed for wire-mesh sensors. They consist of a matrix of electrodes fixed directly to the inner surface of the wall of a flow duct. The presence of a film of liquid is reflected by an electrical current flowing between a pair of electrodes and the strength of the current is a measure of the film thickness. Since electrodes are mounted flush to the surface, this kind of sensor is non-intrusive.
Liquid film sensors were developed in the frame of a PhD project and applied to the wavy annular flow in subchannels formed inside a fuel rod bundle. The sensor is described in the PhD thesis of Manuel Damsohn, PhD Thesis, ETH NO. 19527, Zurich, 2011.
A movie with animations of film sensor measurements can be downloaded from Download here (low resolution) (WMV, 19.8 MB), or Download here (better resolution) (WMV, 48.9 MB)