Studies by Scale Model of the Effects of Various Factors on the Size of Bubbles in the Bubbling through Molten Glass

Abstract

In the bubbling process in glass melting the gas is blown out through the liquid of high viscosity with a considerable velocity and being under the rule of hydrodinamics, the estimation of the size of bubbles by theoretical calculation will be very difficult.
The authors, therefore, carried out the model experiments in order to establish the relations between the size of bubbles at the mouth of nozzle inserted vertically into the molten glass, and the gas velocity, the physical properties of glass, and the nozzle diameter.
In the first place the authors determined the dimensions of cold scale model satisfying the conditions of similitude using the method of dimensional analysis.
As the model liquid millet jelly was used, and the surface tension and the density of glass were assumed to be 300 dyne/cm, and 2.5g/cc respectively. The experiments were carried out under the conditions; viscosity 100-400 poise converted to actual furnace, flow volume 20-65cc/sec, nozzle diameter 0.5-10mm.
The results showed qualitatively but clearly the profound influence of flow volume of gas and the viscosity of glass on the size of bubble. Moreover, it was found that the experimental results could be divided into two groupes bounded by Ih=50, which is a non dimensional term given by the ratio Froude/Raynolds numbers, and represents the influence of bouyancy and viscous force.
Using these experimental formulas the relations between the size of bubble and the factors were made into tables.
Also it was confirmed that the size of bubbles in the prototype were in good agreement with the calculated values using the experimental formulas.