Conjugate Heat Transfer in an Optical Fiber Coating Process

The optical fiber coating process in an axi-symmetric applicator and die system was simulated in this study. Various thermal conditions and process variables are investigated. Ultra-violet (UV) curable acrylates are used for the coating material, whose properties are highly dependent on temperature. Conjugate heat transfer is considered at the moving fiber surface since the fiber constantly exchanges energy with the contacting fluid. The temperature level in the applicator and die is found to increase with fiber speed, the increase being the highest in the die whose wall temperature is kept fixed. This high temperature rise is primarily due to the tremendous viscous dissipation within the fluid, especially in the die. It is important to avoid high temperatures in the fluid because the polymer starts to crosslink and degrade. The fiber temperature at the entrance was also found to be of substantial importance. This work can be used to improve the quality of the coating, particularly its uniformity, and the production rate.