Convective flows in annular passages with the inner core moving at constant speed were investigated for conditions applied to the cooling of optical fiber during the draw process. Temperature dependent gas properties were fully accounted for in the complete set of conservation equations. The geometrical configuration of the model was formulated to reflect experimental conditions previously used : For cooling of the fiber in forced flow. The numerical solution of the conservation equations was validated using experimental measurements. The numerical results were used to predict the variation of fiber temperature at the cooling section exit with respect to relevant draw parameters for aiding and opposing flows. A mean temperature for the gas properties was found, that can be used to. predict within 10% the exit fiber temperature using constant property modeling; The results presented allow estimation of the fiber temperature for a wide rang of operating conditions and cooling section geometries.