Studies on the Model Experiment of the Flow of Molten Glass in a Tank Furnace

Abstract

Many researchers have attempted various model experiments as a method to study the flow patterns or the characteristics of the convection current of molten glass in a tank furnace, as well as the theoretical considerations of the law of similarity. However, the adaptation of the similarity criteria may still be open to criticism.Standing on the experiences obtained from the previous model experiments the authors intend in this paper to scrutinize the law of similarity and to get the practical and convenient method for determining the experimental conditions, with which the law may be satisfied as much as posible. In the last part of this paper some results of model experiments are indicated and the applicability and its limitations are discussed.Considering the conditions which make the three equations governing the behavor of liquid in scale model, i.e., Navier-Stokes equation, the equation of continuity and the equation of energy, similar to those of the actual tank, the similarity criteria being Pr, Gr and Re for the pull current were derived. Furthermore, the authors pointed out that some quantites in these formulae for the model should have the proportional relations to those of the actual tank and the other such as pressure, temperature and time have the linier relations, so these quantities must be selected initially to satisfy the demands.As a model liquid glycerin was used and Gr and Pr numbers for this liquid were determined for vaious concentrations, scales of model and the maximum and minimum temperatures in model. The results are summerized in Fig. 6 which shows the experimental conditions to satisfy the similarity criteria. The maximum and minimum temperatures used above were so determined that the ratio of the viscosities of glycerin at these temperatures in model is equal to that of glass in actual tank. Consequently it is found that, for instance, using 88% glycerin as the working liquid in the 1/30 scale model the applicable temperatures of the liquid are 18.5°C and 56°C against 1200°C and 1500°C in the proto type, and for the 1/50 scale model using 82% glycerin they are 14°C and 57°C.On the experimental technique it is convenient that the temperature distribution of liquid in model is made similar to that of actual tank by the method of adjusting the heating and cooling conditions.From the observations of flow patterns in our experiments it is believed that for the most part of tank the model has a posibility to represent the behavor of molten glass in actual tank fairly well.