Clamp-on flow measurement in cooling circuits
Stationary KATflow 150 flowmeters have been installed in the cooling circuits of the Wendelstein 7-X fusion research project. The clamp-on systems enable reliable measurements of deionised water under extreme temperature and magnetic field conditions.
Four KATflow 150 units with Profibus DP interfaces in a high-temperature application within a fusion reactor
Fusion energy has the potential to provide humanity with carbon-free, unlimited energy and to free us from the constraints of our planet’s limited resources. We are delighted that Katronic’s non-invasive clamp-on ultrasonic flow measurement technology is making a small contribution to the operation of an ambitious experimental research facility: the Wendelstein 7-X, a so-called stellarator, in Greifswald, Germany. Together with the ITER tokamak project in the south of France, these two long-term projects are intended to pave the way for the first fusion power stations of the future. A key factor in the successful application of the flow meter was the Katronic devices’ resistance to the massive magnetic fields that are crucial for confining the high-energy plasma.
The Wendelstein 7-X facility has a ring-shaped design with a diameter of approximately 14 m. It is based on the stellarator principle, in which external coils alone generate the twisted magnetic field used to confine the hydrogen plasma required for nuclear fusion. The required plasma temperatures are generated, amongst other things, via an ICRH (Ion Cyclotron Resonance Heating) system. To achieve this, short-wave radio waves are beamed into the plasma via an antenna; these are absorbed there – much like in a microwave – and thus raise the plasma’s temperature to 150 million °C. This very high temperature, the particle density and sufficient thermal insulation of the plasma from its surroundings are the three essential prerequisites for a successful laboratory fusion experiment using a stellarator magnetic field.
The installation environment for this ICRH antenna comprises eight water-cooled cooling circuits. These are essential technical components for preventing the antenna from overheating whilst fusion experiments are in progress. The water temperature in the pipes, which have an internal diameter of 8 mm, is 150°C at a maximum pressure of 26 bar; the water flow rate for all circuits is 5.4 m³/h. Initially, experiments were carried out using float-type flowmeters to measure the flow rate. However, the influence of the magnetic field from the stellarator coil system was too strong, meaning that this technique proved unsuitable. The scientists involved in the Wendelstein experiments from LPP-ERM/KMS, the Max Planck Institute for Plasma Physics (IPP) and Forschungszentrum Jülich were therefore forced to develop an alternative solution. Due to the deionised water used in the cooling circuits, a second selection criterion was to find a flow measurement system that operates independently of the medium’s conductivity.
Katronic’s KATflow 150 stationary clamp-on flow meter ultimately met all the technical requirements set for a new flow measurement system. All components of the measuring unit were required to be non-magnetic, which was ensured by the plastic housing of the flow meter and the stainless steel housing of the sensors used. Furthermore, there was to be no direct contact with the medium. This was ensured by mounting the transducers using clamp-on technology, and by taking measurements through the pipe walls of the stainless-steel pipes installed in the cooling circuits.
The four KATflow 150 flowmeters installed are performing exceptionally well in this high-temperature application (flow measurements of deionised water at 150°C). The Profibus-DP interface in each unit, as requested by the customer, enables the measurement data to be transmitted at 4 Mbit/s. Thanks to the combined temperature measurement, the scientists are now able not only to verify the flow rate required for cooling the ICRH antenna, but also to read and evaluate the power loss and energy of the radio wave radiation.
Project partners:
Laboratory for Plasma Physics, Ecole Royale Militaire-Koninklijke Militaire School (LPP-ERM/KMS), Trilateral Euregio Cluster (TEC), Brussels
Forschungszentrum Jülich GmbH, Institute for Energy and Climate Research – Plasma Physics, Trilateral Euregio Cluster (TEC)
Forschungszentrum Jülich GmbH, Central Institute for Engineering, Electronics and Analytics
Max Planck Institute for Plasma Physics (IPP), Greifswald
