Effects of Process Conditions of Melting Furnace on Alkali-Free Glass Cleanliness

Abstract

In this study, the effects of process conditions such as air bubbling, top radiation heating and electrode heating in a melting furnace on the cleanliness of alkali-free glass, which is characterized by the residence time and trajectories of tracer particles, is investigated by a reduced physical model. The reduced physical model was made of an acrylic tank, which is similar in shape of the actual glass melting furnace but one tenth in size, with heating electrodes, top radiation heating and air bubbling devices. Silicon oil was used to simulate molten glass. The gas flow rate was set at 6:67 Â 10 À7 Nm 3 /s. The electrode and radiation temperatures were set at 298 K, 323 K, 353 K and 373 K. Residence time, which is the time required for tracer particles to flow from inlet to outlet, was measured to evaluate the cleanliness of the molten glass. The results showed that the effect of bubbling on residence time is larger than that of top radiation heating which is then larger than that of electrode heating when one single process variable is considered. For the effect of the coupling of two process variables, the dual effect of bubbling and radiation is better than that of bubbling and electrode which is in turn better than that of radiation and electrode. As all three devices were all turned on, it was found that the most desirable condition to obtain clean glass is bubbling with electrode temperature of 323 K and radiation temperature of 373 K.

Numerical Study of Fluid Flow and Heat Transfer Behaviors in a Physical Model Similar in Shape to an Actual Glass Melting Furnace and Its Experimental Verification

“…This 3-D model can deal with the effects of electrode heating and gas bubbling simultaneously. A reduced physical model was also established according to similarity theory 9,10) to validate the accuracy and reliability of the numerical model.…”