Development of a miniature electromagnet probe for the measurement of local velocity in heavy liquid metals

Abstract

ABSTRACT Electromagnetic induction is an effective technique for local velocity measurements in heavy liquid metals, such as mercury and lead/lead–bismuth eutectic. In this regard, Ricou and Vives’ probe and von Weissenfluh’s probe are well-known instruments that use permanent magnets. However, the sensitivity and measurement volume of the probes unexpectedly vary because the permanent magnet is demagnetized as the temperature increases up to the Curie temperature. Furthermore, such probes do not work for local velocity measurements over the Curie temperature. In this study, a new electromagnetic probe using a miniature electromagnet was developed as a prototype sensor to overcome such disadvantages of the permanent magnet. The diameter and the length of the sensor were 6 and 155 mm, respectively. The electromagnet incorporated in the sensor was excited by a direct current of 50 mA. The fundamental performance of the sensor was confirmed in a room-temperature experiment by measuring the local velocity of flowing mercury in a square channel. Numerical velocity profiles were calculated and compared with those of the experiment to clarify the validity of the measured velocity profiles. In this paper, the sensitivity and the measurement volume of the probe were assessed. The validity of the measured velocity profiles was confirmed by the calculated results.