Glass fibers drawn from the melt cool primarily by convection, through a boundary layer process that has been the subject of a number of theoretical studies. In the present work, the temperature distribution along such a fiber has been measured under a range of conditions in laboratory-scale system. The measurements were made using a heated thermocouple technique, in which a thermocouple is electrically heated to a temperature near the local fiber temperature; the response of the thermocouple is observed upon slight contact with the fiber. Calibration tests showed this technique could be used reliably for small bodies at temperatures ranging from 400 to 1000 kelvin. We measured the temperatures of glass fibers with drawing speed ranging from 1 m/s to 6 m/s and diameters ranging from 20 to 50 μm. We found our data to be close to, but somewhat lower than, the theoretical prediction based on the von Karman-Pohlhausen boundary layer integration technique. The difference may lie in either the idealizations of the theoretical model or additional cooling due to fiber vibrations. The scaling of the theoretical model nevertheless represents the present data well.
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