Measurement of Ice Movement in Water using Electrical Capacitance Tomography

J. Fan, L. Jing, and L. Shi

Institute of Engineering Thermophysics, Chinese Academy of Sciences, P.O. Box 2706, Beijing 100080, China, Email: jiangfan1@hotmail.com

ABSTRACT

The permafrost with the highest altitude and largest area in the mid and low latitude is located in the Qinghai-Tibet Plateau. As most frozen soils contain ice particles which are very sensitive to temperature and other external parameters, thus influencing the stability of the embankment in permafrost regions, it is very important to develop techniques to prevent damages to railway embankments due to thaw settlement. In this paper, the electrical capacitance sensors are designed to study the freezing front movement in a vessel and ice movement in water, which is the first step to apply the ECT system to the study of frozen soil. Two sensor arrangements are put into use. One is an unclosed electrodes sensor. In this arrangement, eight pairs of electrodes are arranged along the height of the vessel. This sensor arrangement is used to monitor the movement of ice freezing front. A sudden decrease in the measured capacitance is observed when the freezing front advances past the electrodes. The other sensor system is a closed electrode sensor. In this arrangement, the electrodes are attached to the outside of the pipe or vessel, and the cross-sectional distribution of ice and water could be reconstructed from the capacitances measured. As ice moves in the vessel full of water, the ice moving track at the cross section could be reflected thoroughly. All the above results show that the electrical capacitance sensor system can be used to detect and monitor the movement of freeze-thaw boundaries in water, which could provide some data and instructive information for further research.

Keywords electrical capacitance tomography, ice-water interface, two-phase flows, frozen soil