Measuring flow properties

P. Marjanovic, M.G. Jones, Assessment of a new technique for measuring flow properties of powdered materials stored in hoppers, IMechE J. Process. Mech. Eng. 210 (1996) 1-8. 

According to the Rossi-Picesa technique standardized in the USA by ASTMD 569-82, ( The Method of Measuring Flow Properties of Thermoplastic Molding Materials), the flowability of thermoreactive materials is determined by measuring the effort and time of flow in a vertical cylindrical channel of 3.18 0.013 mm diameter and 38 mm in length. Pressure on the material in the 25.4 mm diameter die amounts to 0.62 — 1.03 MPa. 

Schwedcs J. Testers for measuring flow properties of particulate solids. Presented at Reliable Flow of Particulate Solids III, Posgrunn, Norway. 19. ... 

The flow-property or rheological constants of non-Newtonian fluids can be measured using pipe flow as discussed in Section 3.5E. Another, more important method for measuring flow properties is by use of a rotating concentric-cylinder viscometer. This was first described by Couette in 1890. In this device a concentric rotating cylinder (spindle) spins at a constant rotational speed inside another cylinder. Generally, there is a very small gap between the walls. This annulus is filled with the fluid. The torque needed to maintain this constant rotation rate of the inner spindle is measured by a torsion wire from which the spindle is suspended. A typical commercial instrument of this type is the Brookfield viscometer. Some types rotate the outer cylinder. 

Schwedes, J. (2003) Review on testers for measuring flow properties of bulksohds. Gtamdar Matter, 5(1), 1 3. www.texturetechnologies.com. 

J. Schwedes, Testers for Measuring Flow Properties of Particulate Solids, Proceedings of the International Symposium Reliable Flow of Particulate Solids III, Telemark College. Porsgrunn, August 11 - 13, pp. 3 - 40,1999. 

Very often a silo is build without knowing the flow properties and during operation a lot of problems occur. To solve these problems first the flow properties have to be measured and then the silo has to be adjusted to the measured flow properties in such a way that the problems disappear. 

Another method to measure flow properties after application involves the application of microdielectric measurements that have shown promise for characterizing fihn formation and cure (5,10-13). In this technique, the paint is applied to a thin, flat sensor connected to a frequency generator, an impedance analyzer and a computer. The sensor monitors the dielectric properties of the paint film at and near the interface between the sensor and the coating. The dielectric parameter used to estimate flow is called ion viscosity, but really is electrical resistivity rather than a trae viscosity. Ion viscosity is a measure of both the number and mobility of ions in a specimen. It is affected by changes in temperature, loss of solvent, crosslinking and other chemical reactions, formation of physical structure (such as by a thixotrope), ionic impurities, and ionic additives. The advantage of this technique is that measurements can be made in situ during application, flash, and the bake. 

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