Transient Eddy Current Flow Meter (TEC-FM)
HZDR has been working on the development of calibration-free, inductive velocity sensors for liquid metals for several years now. This type of sensor is called Transient Eddy Current Flow Meter (TEC-FM). Initially an external TEC-FM was developed to measure the velocity at the fluid boundary from the outside, without direct contact with the liquid metal. This sensor is especially useful for small or shallow pipe flows. In order to perform local velocity measurements in large pipes or liquid metal pools, an immersed version of the sensor has been developed, which is called ITEC-FM. It can be used for ambient temperatures up to 700 °C. Contrary to the most inductive flow rate sensors, the TEC-FM yields results that are independent of the electrical conductivity or temperature of the liquid metal and therefore, no calibration of the sensor is necessary.
Although there are some major differences in the structure of the external and immersed TEC-FM, they use the same physical principles. The primary coil or coils are used to imprint an eddy current system into the liquid metal which it then advected with the flow. With the help of the secondary coils, the position of a distinctive point like the zero crossing or the pole of the magnetic field of the eddy current system is tracked and recorded. The flow velocity can then be obtained from the progression of the distinctive point.
|Figure 1: Basic structure of the TEC-FM|
|Figure 2: Basic structure of the immersed TECFM|
With the external sensor it is not only possible to perform contactless measurements of the flow velocity of liquid metals, it is also possible to measure the translational or rotational speed of metallic solids almost instantaneously. The immersed TEC-FM can be used for velocity measurements in large pipe flows or liquid metal pools, for example in liquid metal cooled reactors. The sensors have been tested successfully in Galinstan(GaInSn), sodium and with rotating copper- and aluminium disks.
- Commissariat à l’énergie atomique et aux énergies alternatives (CEA, Frankreich)
Ratajczak, M.; Hernández, D.; Richter, T.; Otte, D.; Buchenau, D.; Krauter, N.; Wondrak, T.
Measurement techniques for liquid metals
IOP Conference Series: Materials Science and Engineering 228, 2017
Krauter, N.; Stefani, F. :
Immersed transient eddy current flow metering: a calibration-free velocity measurement technique for liquid metals
Measurement Science and Technology 28(2017), 105301
Krauter, N.; Forbriger, J.; Stefani, F.
Transient eddy current flow metering: a calibration-free measurement technique for liquid metals,
Proceedings of the 10th PAMIR International Conference Fundamental and Applied MHD, 2016
Forbriger, J.; Stefani, F.
Transient eddy current flow metering
Measurement Science and Technology 26, 2015
- Patent „Method and system for calibration-free determination of a flow velocity of an electrically conductive fluid“ PCT/EP2016/076967