SOLIDIFICATION AND MELTING OF GALLIUM IN THE PRESENCE OF A MAGNETIC FIELD -EXPERIMENTAL SIMULATION OF LOW GRAVITY ENVIRONMENT -

摘要

Phase change in a simulated low gravity environment is the central topic of this research work. The application of a transverse magnetic field gives rise to Lorentz forces that can dampen the convective flows especially the buoyancy driven flows. The flow suppression depends on a dimensionless parameter namely the Hartmann number. This paper presents the experimental results for sidewall solidification and melting and therefore, addresses the fixed solid phase conditions. Gallium is used as phase change material (PCM) and both melting and solidification processes are investigated. The effects of an applied magnetic field on phase change rate and on the shape of the solid/melt interface are studied. The solid thickness is measured via ultrasonic techniques and the solid/melt interface is mapped using florescent light shadowgraphy through a transparent window. The presented data consist of temperature history, ultrasonic detection of the interface, florescent light shadowgraphy and solid phase volume fraction. The presence of the magnetic field had a marked effect on melting and natural convection whereas; phase change convection was noticeable in the solidification cases.