Pumping zone

Union Carbide Patents. During World War II, Union Carbide and Carbon Corporation patented a process (24) having some features in common with the German process described above. The Union Carbide process as patented is illustrated in Figure 15. The continuous process consists essentially of two reaction zones followed by a milling-pumping zone. 

The final zone of an extruder is the metering section (also known as the pumping zone). The principal function of this zone is to ensure a steady output of molten polymer at a constant pressure. The longer the metering zone, the greater the pressure built up within it. Channel depth is constant to ensure a uniform transport rate, which helps reduce pressure fluctuations arising in the mixing zone. 

Fig. 15. Calculated up-pumping zone width, adapted from ref. [51]. As the shock pressure increases, the up-pumping rate increases but the shock moves faster, so the zone width changes by less than a factor of two for shocks in the 0-10 GPa range.

Fig. 12.1 Different zones in a twin-screw extruder (A) fully filled zone (pump zone), (B) partially filled zone. (C) melting zone. (D) feed zone.

The number of applications in flow analysis is increasing, and several are related to modern concepts such as multi-commutation, multi-pumping, zone fluidics, and bead manipulation. This is perhaps the most important consequence of the favorable characteristics of the flow system, often leading to improved sample treatment and quantification. 

From the velocity profile in the down-channel direction the throughput of the pump zone of a single-screw extruder can be obtained by integration ... 

The pump zone, completely filled with material where pressure is built up and where the material is transported toward the die... 

Here AP is the pressure drop per chamber, caused by the pressure in front of the die, and is the Newtonian viscosity. These two dimensionless groups for throughput and pressure are very powerful. When these groups are used, the characteristics for the completely filled pumping zone of twin-screw extraders are straight Unes that are independent of viscosity and speed of rotation of the screws. Figure 6.9 presents an example of these Unes and their dependence on the size of the... 

The equation for the motor power in the pump zone can be written as ... 

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