Inertia and gravitational effects in extrusion dies for non-Newtonian fluids

✍ Scribed by William K. Leonard

• Publisher: Society for Plastic Engineers
• Year: 1985
• Tongue: English
• Weight: 696 KB
• Volume: 25
• Category: Article
• ISSN: 0032-3888
• DOI: 10.1002/pen.760250910

✦ Synopsis

Abstract

An analysis is presented which allows the sheet or film die designer to estimate when inertial and gravitational effects are important. General theoretical equations are developed for end fed dies with arbitrary variation of the cavity cross sectional shape, cavity taper, slot length, and gap over the width. The method assumes viscous flow and a two dimensional approximation for the cavity flow. For fluid flow properties, it is assumed only that the apparent viscosity is a single valued function of the shear rate. In the important special case of constant die geometry and power law fluids, three dimensionless numbers plus the power law index are the parameters controlling the uniformity of flow from the die. Results are presented that illustrate when die orientations with respect to gravity and when fluid inertia are important. When they are not, simple expressions for die inlet pressure and uniformity index are given.