Parallel flights

In SSEs the number of parallel channels equals the number of parallel flights. In a TSE the number of parallel channels is larger than the number of flights. For example, as... 

The power consumption in the clearance is directly proportional to the number of parallel flights, the local viscosity, and the flight width, and is inversely proportional to the radial clearance. It will be shown later that a substantial portion (in some cases 50% or more) of the total power consumption is consumed in the clearance. Therefore, the geometry of the flight clearance becomes an important geometrical variable when It comes to minimizing power consumption. 

Axial melting length versus helix angle fori, 2, and 3 parallel flights... 

The effect of the number of parallel flights in the feed section has already been discussed in Section 7.2.2. Increasing the number of parallel flights reduces the open cross-sectional area of the channel (see Fig. 8.18) and increases the area of contact between the solid bed and screw. Both of these factors have a negative impact on the solids conveying performance, particularly when the helix angle is relatively small. The volumetric efficiency shown in Fig. 8.18 is the open cross-sectional area relative to the total area between the root of the screw and the barrel. 

Note that the material is displaced by an axial distance of three times the pitch when it reenters the screw. Thus, in a double-flighted geometry, there are three more or less independent down-channel flows. When the number of parallel flights is p, the number of independent down-channel flows Oj is ... 

Thus, at a certain diameter, the open area is primarily a function of the number of parallel flights p and the intermeshing angle aj see Fig. 10.18. 

This equation tells us that for a fixed barrel diameter the open area depends on the number of parallel flights and the angle of intermesh, a. ... 

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