Thermal Studies of Contracting Gas Bubbles in Molten Glass
The behaviour of oxygen gas bubbles in a barium-aluminium alkali-silicate glass is described. The contracting sphere equation was found to describe the kinetics of bubble contraction in a series of isothermal experiments performed in the temperature range 850–1400 C. The experiment involved direct photographic recording of bubble size at recorded time intervals of a bubble rising freely in a bath of molten glass. Use was made of reduced time plots to indicate that the process was isokinetic over this range of temperature and that the contracting sphere equation gave the closest fit with the experimental data. On the basis of existing theoretical treatments this would indicate a phase boundary controlled process rather than a diffusion controlled kinetic process. The activation energy for the process is 142 kJ and the pre-exponential term is 0.925 cm s-1 if the experiments are recorded in terms of change in diameter (cm) with time (s).
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