Measurement of velocity in high-temperature liquid metals

Abstract

There is a paucity of methods available for the measurement of velocity in high-temperature liquid metals. This is due to the hostile environmental conditions which characterize liquid metals. This article proposes and appraises a new velocity measurement technique for liquid metal flows at high temperatures. The melting rates of metallic spheres in metal baths of the same chemical composition as the spheres are studied under isothermal conditions. It is dem-onstrated that the metallic sphere can be used as a probe for measuring the average velocity in a metal flow system over a distance equivalent to the diameter of the sphere. The system that was chosen for study is the commercial purity aluminum bath. The experimental calibration setup examined three different elements: (a) it introduced a stationary sphere in a metallic bath of a given temperature and compared its melting rate with that of a moving sphere with known external velocity along the periphery of a circle in a metallic bath of the same temperature; (b) three different sphere diameters were used; and (c) a range of bath temperatures was investi-gated. By studying the effect of these three elements concurrently, it was possible to determine the interplay of these elements. Results showed that the sphere melting time was related linearly to the flow velocity for the range of velocities of 0 to 40 cm/s and for bath superheat up to 100 °C. In order to verify the accuracy of the results obtained by the proposed technique, a comparison was undertaken between mathematical predictions and experimental results of a fluid flow field obtained in an AC induction furnace with molten aluminum. These predictions were made by solving numerically the relevant differential equations under the appropriate boundary conditions. The experimental results attained using the proposed technique were in close agreement with those from the mathematical predictions.