Example for the Design of a Pressure Build-Up Zone

The following numerical example illustrates the effect of pitch selection on energy dissipated in the pressure build-up zone. A nozzle pressure of 50 bar has to be generated, the viscosity of the polymer at the machine s head is 200 Pa s and a double-flighted machine with the following properties should be considered  

Barrel internal diameter D Centerline distance A Radial screw clearance 8 Reciprocal screw clearance s 57.350 mm 48.000 mm 0.170 mm 0.525 mm 

There are screw elements available with a pitch of 40 mm of the two screws were determined experimentally [4], and 60 mm. The feed parameters 

In example 1, a volume throughput of 300 1/h is pumped at a rotational speed of 300 rpm. Eqs. 7.2 to 7.10 and the typical physical properties of density p=1000 kg/m3 and specific heat capacity c=2000 J/kg-K are used to calculate the back-pressure length, pumping efficiency, energy input and temperature rise in the polymer for the two available screw elements. 

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