Measurement techniques for liquid metals
In metallic melts mainly the flow structure and, in the case of gas injection, the localization of gas
bubbles are the features of interest. While in the laboratory often low-melting alloys like gallium-
indium-tin are employed, in the industry metallic melts with temperatures of 1600°C can be
encountered, that additionally can be chemically aggressive. Depending on the scenario, invasive,
non-invasive or contactless measurement techniques are applied.
Applying well-suited measurement techniques enables
- a better understanding of generic and industrial flow problems,
- realtime monitoring of flow coditions in industrial plants, making exact process control possible
- increases process efficiency in terms of energy input and process throughput as well as
Contactless Inductive Flow Tomography (CIFT)
This measuring method was developed in 2004 at the Helmholtz-Zentrum Dresden-Rossendorf and enables the reconstruction of global melt flows in containers. It can, for example, be used in continuous steel casting or crystal growth.
Ultrasound Doppler Velocimetry
The ultrasound Doppler velocimetry is a method for the non-invasive measurement of local flow velocities and well suited for the application at metal melts. It is one of the essential flow measurement techniques of magnetohydrodynamics and as such it is continuously enhanced from HZDR for the application at liquid metals, especially for multi-dimensional field measurements and measurements at hot metal melts.
Eddy Current Flow Meter
The Eddy Current Flow Meter is a robust and reliable sensor for inductive flow rate measurements in liquid metals for ambient temperatures up to 700 °C. It is an invasive Sensor which is immersed into the liquid metal in order to perform local flow rate measurements in the vicinity of the sensor. It is therefore especially suited to measure the flow rate in large liquid metal pools or pipes with high diameters. At HZDR, several miniaturized versions of this sensor have been developed and tested.
Transient Eddy Current Flow Meter (TEC-FM)
Transient Eddy Current Flow Metering is a new inductive measurement technique for the calibration free velocity measurement of liquid metal flows or metallic solids. Two different sensors have been developed at HZDR: The external sensor can be used for contactless velocity measurements and the immersed sensor can be placed directly into the liquid metal do perform local velocity measurements in the vicinity of the sensor.
X-ray radioscopy is an important diagnostic tool for the in-situ studies of solidification processes and liquid metal two-phase flows. Based on the local density differences this technique delivers at least qualitative pictures of the flow pattern.
Inductive level measurement
The high electrical conductivity of liquid metals permits the measurement of the surface position and shape of a melt in a container using the induction of eddy currents. An alternating magnetic field is applied and the resulting secondary magnetic field is measured using gradiometric induction coils.
Bubble detection in liquid metals
The high electrical conductivity of liquid metal can be exploited for a inductive contactless method for bubble detection.