Abstract
The detection of bubbles in liquid metals is important for many technical applications. The opaqueness and the high temperature of liquid metals set high demands on the measurement system. The high electrical conductivity of the liquid metal can be exploited for contactless methods based on electromagnetic induction. We will present a measurement system which consists of one excitation coil and a pickup coil system on the opposite sides of the pipe. With this sensor we were able to detect bubbles in a sodium flow inside a stainless steel pipe and bubbles in a column filled with a liquid Gallium alloy.
Highlights
Bubble detection and void fraction measurement is of huge interest in two-phase flow research and in industrial applications like continuous casting of steel [1], liquid metal cooled reactors or cracking of Methane and Ethane into hydrogen inside a liquid metal reactor [2]
In order to reduce the complexity of this system for detecting bubbles in a pipe filled with liquid metal, we developed a new system consisting only of one excitation coil and one planar gradiometer coil on the opposite sides of the pipe [6]
In order to evaluate this new measurement system at higher temperatures, we mounted the sensor on a vertical pipe with dimension of 50 mm × 45 mm at the NATAN [12] sodium loop at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR)
Summary
Bubble detection and void fraction measurement is of huge interest in two-phase flow research and in industrial applications like continuous casting of steel [1], liquid metal cooled reactors or cracking of Methane and Ethane into hydrogen inside a liquid metal reactor [2]. In case of the cold model experiments the gas distribution in a liquid metal two-phase flow in a pipe is reconstructed by solving a non-linear inverse problem for magnetic field data recorded by 8 sensors. The planar gradiometer consists of two pickup coils positioned on top of each other which are wound in opposite direction and are connected in series In this setup they are only sensitive to any asymmetric magnetic field distribution with respect of the two receiver coils over the height of the pipe. The primary objective of this sensor is the detection of bubbles which are floating in the liquid metal and traversing the sensitive region of the sensor This could be important for the leakage detection in sodium/water heat exchangers. In this paper we will briefly describe the working principle of the sensor and present first measurements in the eutectic alloy GaInSn and in liquid sodium
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