Predicting heat and mass transfer to a growing, rotating preform during soot deposition in the outside vapor deposition process

During the manufacture of optical fibers using the outside vapor deposition (OVD) process, porous soot preforms are made by depositing soot onto a rotating cylindrical target from a soot-laden flame traversing along the target axis. The dominant mechanism of soot deposition in the OVD process is thermophoresis, which is the tendency of particles to migrate down the local gas temperature gradient. Accurate methods to estimate the heat and mass transfer rates from the flame to the growing preform are critical, as these rates dictate important preform characteristics. The heat and mass transfer during the OVD process are coupled due to particle thermophoresis and growth of the preform. We here present methods to predict the growth rate of a rotating preform along with the evolution of temperature profile at different radial locations within the preform for specified process parameters of flame temperature, burner traverse speed and number of burners. Sensitivity of preform temperature profile and deposition rate to each of the process parameters is presented, along with the critical discussion of our principal results.