Effect of Flight Width

The results shown in Figs. 8.25 and 8.26 are for a standard radial clearance of 0.001 D. 

The contribution of the power consumption in the clearance rises dramatically when the power law index increases. When the fluid is Newtonian, around 80% of the total power is consumed in the clearance Thus, problems with excessive power consump- 

Considering that the flight width in the feed section is generally about 0.1 D, Eq. 8.79 can be written as  

Based on these considerations, a new screw design was recently developed to reduce power consumption in materials like LLDPE the screw is often referred to as the LL-screw [4, 5]. 

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