An experimental and theoretical study of the cooling of a thin glass fiber during the formation process

Abstract

The cooling of a thin, moving glass fiber was studied through both experiments and theoretical method in the present thesis. An experimental system was built at a laboratory scale, which included a glass fiber production subsystem, a temperature measurement subsystem, and a thermocouple temperature control subsystem. A heated thermocouple technique was adopted to measure the temperature distribution of the glass fiber along its drawing direction. Data were collected for diameters ranging from 20 to 50 micrometers and speeds from 1 meter per second to 6 meters per second. Experiments were performed both with and without water spray cooling of the fiber. A comprehensive analysis was performed to estimate the uncertainty in our experiments. The analysis shows that, without water spray, the 2a uncertainty is 14.8%, and with water spray, it is 15.3%. The major uncertainty comes from the uncertainty of the thermocouple probe. For theoretical modeling, the von Karman-Pohlhausen boundary layer integral technique was used to predicting the cooling rate of the fiber. The model considers the effects of water spray, variation of drawing speed, fiber diameter, environment parameters, and initial conditions, extending earlier work on the subject. The comparison between the experimental data and the theoretical prediction shows integral methods produce the correct trends, but show systematic disagreements with the data. The models with and without spray show similar levels of disagreement. The direction and magnitude of these disagreements are system dependent.

(cont.) Potential causes may include fiber vibration effects, boundary layer transition, and measurement uncertainties. Thus, future work should focus on measuring/modeling the vibration effect and determining the amplitudes/frequencies of the vibration (which are expected to be system dependent). Incorporation of spray dispersion effects is also required for improved modeling.