Screw pumps flow rate

Campbell, G.A., Wang, C., Cheng, H., Bullwinkel, M., te-Riele, M.A., Investigation of Flow Rate and Viscous Dissipation in a Single Screw Pump-Extruder, Int. Polym. Process., 16, 323 (2001)... 

All of the data in Fig 7.5 were analyzed using linear regression. The summation of the helix and core-regressed flow rates are plotted in Fig. 7.5 as the red dotted line. The experimental superposition for the flows induced by the screw elements essentially overlaid the regression line for the screw configuration rate. Thus, it was concluded that the helix is the pump in the single-screw extruder, and core rotation reduces the flow by dragging the fluid back toward the extruder inlet. 

Experiments were run on a laboratory screw pump to evaluate the fluid temperature increase of an enclosed fluid as a function of element rotation time. For this case, the device was similar to that shown in Fig. 7.4, and the discharge was blocked using a valve. The blocked flow caused the rate to be zero and = 0 p. Both the device and the fluid were at room temperature at the start of each experiment. The task at hand is to use the information below and the equations presented in Chapter 7 to calculate the temperature increase for the fluid for a total time of 30 seconds in three-second increments. The dimensions of the single-flighted extrusion device are provided in Table 7.5. 

The cross channel flow is derived in a similar fashion as the down channel flow. This flow is driven by the x-component of the velocity, which creates a shear flow in that direction. However, since the shear flow pumps the material against the trailing flight of the screw channel, it results in a pressure increase that creates a counteracting pressure flow which leads to a net flow of zero1. The flow rate per unit depth at any arbitrary position along the 2-axis can be defined by... 

Single-screw Pump with Inner Recycle A constant channel-depth single-screw pump with a linearly rising pressure has a hollow shaft, as shown in the accomapny-ing figure, connected to the channel such that part of the flow is recycled. Assuming isothermal Newtonian flow (a) derive and expression for the flow rate of the extruder, and (b) for the recycle rate. 

The valves supplied with these pumps showed an erratic behavior at low flow rates, mainly due to a too large diameter of the valve balls and poor design of the valve seats and valve chambers. New pumpheads and valves were therefore developed, manufactured and mounted on the pumps. The heads and fittings were made from PVDF with valve seats and 3 mm diameter balls in acid resistant steel. On these pumps the stroke length has to be set mechanically and this set-screw was modified so that it could be turned by a simple manipulator, if necessary. The electronic frequency control was modified for remote operation. 

This particular fermentation is performed in 1+00 liter batches. Tangential flow filtration was carried out with a Pe licon cassette (Millipore Corp.). The filtration area was 25 ft using a 100,000 molecular weight cut off ultrafiltration membrane. The inlet pressure was maintained at 1+0 psig while the outlet pressure was 25 psig and recirculation rates of the cell suspension were 3 5 GPM tangential to the upstream membrane surface. Pumping of the cell suspension was performed with a Moyno screw pump. 

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