Hopper flow factor

H 9 ) is a dimensionless function derived from first principles and is given by Figure 7 [for the complete derivation of H 0 ), which is beyond the scope of this chapter, see Ref. 4]. /ent, with units of force/area, is the unconfined yield strength at the intersection of the hopper flow factor (ff, a derived... 

If the hopper-flow factor lies above the powder-flow function, cohesive arching is not possible with the material in that hopper. If the hopper factor lies below the powder-flow function, arching of material in the hopper is possible even for large-outlet sizes. 

The hopper flow factor, ff, relates the stress developed in a particulate solid with the compacting stress acting in a particular hopper. The hopper flow factor is defined as ... 

Knowing 3, w/ and 0, the hopper flow factor, //, can be fixed. The hopper flow factor is therefore a function both of powder properties and of the hopper properties (geometry and the material of construction of the hopper walls). 

Knowing the hopper flow factor and the powder flow function (cFy versus ac) the critical stress in the arch can be determined and the minimum size of outlet found corresponding to this stress. 

The hopper flow factor, //, is a function of b, w/ and 6 and can be calculated from first principles. However, Jenike (1964) obtained values for a conical hopper and for a wedge-shaped hopper with a slot outlet for values of b of 30°, 40°, 50°, 60° and 70°. Examples of the flow factor charts for conical hoppers are shown in... 

Figure 10.18 (a) Hopper flow factor values for conical channels, d = 30°. (b) Hopper flow... 

Using the flow factor chart for 3 = 30° [Figure 10.18(a)] with = 19° and a 3° margin of safety gives a hopper flow factor, // = 1.8, and the semi-included angle of hopper wall, 6 = 27.5° (see Figure 10W1.3). 

Which quantity describes the strength developed by a powder in an arch preventing flow from the base of a hopper How is this quantity related to the hopper flow factor ... 

---