Unwound screw channel

Figure 7.59 Schematic diagram of an unwound screw channel. From Z. Tadmor and C. G. Gogos, Principles of Polymer Processing. Copyright 1979 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

Fig. 9.3 Top view of an unwound screw channel indicating the oblique ends of the channel. The significance of this geometrical end-effect correction factor is of the order n sin 6 cos 0/(L/D).

FIG. 21-145 The unwound screw channel, illustrating the barrel moving at a velocity V and at a angle 6 with respect to the down channel direction x. The barrel slides over the solids at a relative velocity V, resulting in a frictional shear stress along the wall of and a solids conveying angle of 0. 

Figure 12.15 Unwound screw channel showing coordinate system and principle velocity components, directions, and dimensions.

Figure 7.2 Transforming the Cartesian reference frame a) cylindrical cross section of the screw and barrel with flow out of the surface of the page, and b) the unwound rectangular channel with a stationary barrel and the Cartesian coordinate frame positioned on the screw, is the velocity of the screw core in the z direction and it is negative...

Fig. 6.49 The unwound helical channel segment forming a single chamber of the counterrotating twin screw.

Fig. 15 Schematic diagram of the unwound helical channel of a single-screw extruder.

A three-dimensional simulation method was used to simulate this extrusion process and others presented in this book. For this method, an FDM technique was used to solve the momentum equations Eqs. 7.43 to 7.45. The channel geometry used for this method was essentially identical to that of the unwound channel. That is, the width of the channel at the screw root was smaller than that at the barrel wall as forced by geometric constraints provided by Fig. 7.1. The Lagrangian reference frame transformation was used for all calculations, and thermal effects were included. The thermal effects were based on screw rotation. This three-dimensional simulation method was previously proven to predict accurately the simulation of pressures, temperatures, and rates for extruders of different diameters, screw designs, and resin types. 

We are now in position to calculate the remaining unknowns for the single-screw extruder, which are N and pQ. Using the data for the twin-screw system given in Table 8.1 we can calculate N 2 (= Ti/tfi). The unwound channel lengths are... 

Figure 15.12 Unwound channels of three-tip screw elements. Arrows show the motion of the fluid as it is transferred from one screw to the other in the intermeshing region. (From Ref 20.)...

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