The Method Based on Electromagnetic Sensor for Measuring of Sodium Flow Rate in a Heat Pipe
The electromagnetic sensor design and method of liquid flow measuring in the vertical sodium heat pipe 100 mm diameter and 10 m length at operating temperature 550–650оС are described. The heat pipe was supplied with capillary structure only in the evaporation zone, i.e. it was a thermosyphon with nonseparated opposite flows of liquid and vapor.
Magnetic field of the sensor was produced by permanent magnet, made of thermostable alloy, which is efficient up to 600 оС. Flow measurements at three cross sections of the heat pipe, at four «points» of circumference of each section, were carried out. Significant fluctuations of the local flow rate values were observed. Maximum amplitude of the fluctuations exceeds the average value of the flow rate up to 2-3 times. Negative values of the local flow rate were observed. It means that liquid sodium flowed against the gravity force, and this indicates that the liquid sodium entrainment caused by vapor counter-flow, the speed of which was about 80 m/s, took place.