Extrusion rectangular channel

Traditionally the fluid mechanics of the extrusion process are summarized by the simple plate model illustrated in Fig. A7.1 and as described in Section 7.4. The motion of the screw is unchanged, but the reference frame has been moved to transform the problem to a fixed boundary problem for the observer. The flow in the rectangular channel is reduced into the x-direction flow across the channel and the z-direction flow down the channel. 

In practice, few extrusion dies are designed with square channels at the exit. However, many are designed with a rectangular channel in the lip region exiting the die. The effect of Reynolds number on the extrudate swell from such shapes appears to have been heretofore unreported. 

We consider a co-extrusion die consisting of an outer circular distribution channel of rectangular cross-section, connected to an extrusion slot, which is a slowly tapering narrow passage between two flat, non-parallel plates. The polymer melt is fed through an inlet into the distribution channel and flows into... 

The fabrication of ceramic monoliths is performed mainly via extrusion techniques [9] resulting in usually elliptic or squareshaped monoliths. Cell densities as high as 1600 cells per square inch (cpsi) are achieved [9], which corresponds to a channel width of about 500 pm of the mostly rectangular or hexagonal channels. Typical key features are 75% porosity and a geometric surface area of 2.8 m /1 for 400 cpsi for ceramic monoliths [10]. The thermal shock resistance amounts to 800°C and higher. 

Apart from rectangular and annular extrudates, there is a tremendous variety of extruded profiles with other shapes. Profile dies usually describe dies used to produce shapes other than rectangular or annular. Profile extrusion is often the most difficult type of extrusion. This is, to a large extent, due to the fact that it is very difficult to accurately predict the required geometry of the flow channel that will yield an extruded product of proper shape and dimensions. 

Ceramic monoliths (see Figure 6.1) are produced mainly by extrusion techniques [130]. The cross-section of the monoliths is usually elliptic or square. Up to 1600 cells per square inch (cpsi) may be achieved by this technique [130], which corresponds to a channel width of about 500 pm. The shape of the channels is usually rectangular or hexagonal. More than 75% porosity may be achieved in ceramic monoliths [136]. The geometric surface area is 2.8 m for 400 cells per square inch... 

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