Summary

A theory has been developed, based on a physical model, to describe the behaviour of non-cohesive granular material inside a ver-tical screw conveyor. By use of this theory, relationships have been derived between di-mensionless numbers for capacity, power con-sumption and efficiency. These relationships, or characteristics, are compared with the re-sults of experiments carried out with two models of vertical screw conveyors, one of 50.8 mm and the other of 162.0 mm diam-eter _ The agreement between the calculated and the measured values of capacity and power consumption was within 5 and 9% respectively. The investigation was extended to a screw with an inclined screw blade, because one might expect that this would result in a steep-er upward motion of the granules and thus would lead to an increased capacity _ It ap-pears, however, that this type of screw has no practical advantages over the normal one, and it is therefore not treated here. Two other simpler theories were also devel-oped, one based on a simphfied physical model [27] and the other on the conveying of a single granule [28] _ It appears that the simpler theories do not agree with the experi-ment as well as the one developed in this dis-sertation does, the theory of the single gran-ule producing the greatest discrepancies _ With the latter theory, however, the capacity can be reasonably well approximated when the ‘degree of fullness ’ S 60%. The influence of the inlet section on the * Essentials from ‘The vertical screw conveyor ’ by th