Screw conveyors are used to transport and elevate bulk materials over relatively short distances. There are several important issues, which need to be considered in designing such equipment. They are as follows.

• How does one ensure an even draw down of material from the supply hopper (in the direction of the screw)?

• How is the transport rate affected by the incline angle of the screw?

• How do material properties (friction, elasticity, size and shape distribution) affect the flow?

• How much degradation is caused to the material by the high forces imposed on particles in the gap between the screw and surrounding shell?

The first two issues are the focus of this particular example.

Here, we model an inclined screw conveyor with triangular slot feed hopper and an end discharge (McBride, 2002). The screw has a constant pitch, a diameter of 200 mm and is inclined at 45 and the particle sizes are uniformly distributed between 20 and 25 mm. Figure 4 shows the screw rotating at 2.5 Hz. The particles are shaded in vertical layers in the hopper to show their starting positions. The measured mass flow rate is 16 kg/s. Initially, the particles drop from the hopper into the empty space around the screw. They are then transported along by the screw. New particles are then drawn down from the hopper to replace those transported along by the screw. This draw down is observed to be heavily weighted towards the particles at the back of the hopper...