Entrance region flow of polymer melts

An experimental study has been made to investigate polymer melt flow in the entrance region of a circular tube. For the study, a capillary rheometer was used to measure wall normal stresses in polymer melts in the reservoir and along the axis of the capillary. In order to investigate the influence of reservoir diameter on the entrance pressure drops, reservoir‐to‐capillary diameter (DR/D) ratios of 3, 6, 9, and 12 were used, with the capillary length‐to‐diameter (L/D) ratio being 20 and the capillary diameter being 0.125 in. Analysis of the experimental data shows that the entrance pressure drop increases and then levels off as DR/D ratio is increased. A correlation between the dimensionless entrance pressure drop and Reynolds number has been obtained, which follows the creeping flow analysis by Weissberg over the range of the area contraction ratio studied, 0.00694 <β< 0.111.