Therefore, the channel geometry (manifold) of a coat hanger die should be optimized in such a way that a uniform velocity distribution at the die exit is obtained without excessively increasing the pressure drop across the die.
The above optimization approach is applied to achieve the optimal design of a wire coat hanger die geometry which enables a good performance with a wide range of materials and multiple operating conditions.
Instead of the flat rear wall of a coat hanger die
, it has a rounded back wall to provide higher output of degradable resins like PVC.
Smith, Tucker and Tortorelli (8, 9) modeled Newtonian and non-Newtonian isothermal flow in a coat hanger die
using a finite element (FE) implementation of the generalized Hele-Shaw 2-dimensional approximation, and optimized the die to minimize pressure drop subject to exit flow uniformity being within a set tolerance.
This number of elements is much more than necessary for accurate determination of the flow field in a coat hanger die (1, 2, 8).
The dip and rise in the profile just before the drop to zero flow on the sides is common in coat hanger dies with shear thinning polymers (1, 2, 8, 9).
The coextrusion of a symmetrical A/B/A structure in a single manifold coat hanger die is examined.
The coextrusion of two "polymers" through a single manifold coat hanger die is examined for the first time using a fully three-dimensional analysis.
12 shows the 3-D parallel projection of the tapered coat hanger die
with a transition length of 3.
In so-called coat hanger dies
, the shape of the triangular dam between the manifold and the exit, and the change in manifold diameter, determine the uniformity of flow.
In the analyses of the flow in coat hanger dies
, most numerical methods deal with a 2-D geometry, but only a few of them have considered non-isothermal flows.
Winter and Fritz (16) presented a new theory for design of coat hanger dies
, with circular- or rectangular-section manifolds.