Measurement of Flow Properties

Whenever a process engineer uses flow property data, he should know on what instrument and how these data were determined in order to properly assess the validity of the data. Instruments to determine flow properties are generaliy referred to as rheometers. The rheometers that wiii be briefly described in the next few sections are the capiiiary rheometer, the meit indexer, the cone and plate rheometer, the slit die rheometer, and dynamic mechanicai rheometers. For a more detailed description of these and other rheometers, the reader is referred to the literature [64-66]. A brief but good survey of commerciai rheometers was presented by Dealy [92]. 

---

Chapter HI relates to measurement of flow properties of foods that are primarily fluid in nature, unithi.i surveys the nature of viscosity and its relationship to foods. An overview of the various flow behaviors found in different fluid foods is presented. The concept of non-Newtonian foods is developed, along with methods for measurement of the complete flow curve. The quantitative or fundamental measurement of apparent shear viscosity of fluid foods with rotational viscometers or rheometers is described, unithi.2 describes two protocols for the measurement of non-Newtonian fluids. The first is for time-independent fluids, and the second is for time-dependent fluids. Both protocols use rotational rheometers, unit hi.3 describes a protocol for simple Newtonian fluids, which include aqueous solutions or oils. As rotational rheometers are new and expensive, many evaluations of fluid foods have been made with empirical methods. Such methods yield data that are not fundamental but are useful in comparing variations in consistency or texture of a food product, unit hi.4 describes a popular empirical method, the Bostwick Consistometer, which has been used to measure the consistency of tomato paste. It is a well-known method in the food industry and has also been used to evaluate other fruit pastes and juices as well. 

Schwedes J, Schulze D. 1990. Measurement of flow properties of bulk solids. Powder Technol. 61 59-68. 

Rao, M. A. 1977b. Measurement of flow properties of fluid foods—developments limitations, and interpretation of phenomena, y. Texture Stud. 8 257-282. 

Figure 3-24 A Schematic Diagram of In-Line Measurement of Flow Properties with an Ultrasonic Doppler Velocity Meter.

Characterization of powders is essential to quality control of raw materials, active or excipient, in order to maintain product uniformity. Flow-property studies of powder materials facilitate the scientific design of formulations and processing equipment, such as the design of mass-flow hoppers. This article reviews the flow properties of powder materials. The factors affecting the flow properties of solids are briefly discussed first, followed by measurement of flow properties. 

MEASUREMENTS OF FLOW PROPERTIES Flow through an Orifice... 

Nqvist, H. Measurement of flow properties in large scale tablet production. Int. J. Pharm. Tech. Prod. Mfr. 1984, 5 (3), 21-24. 

Measurement of Flow Properties A summary of the flow properties that need to be measured to obtain the equipment design parameters required for consistent, reliable flow. 

The primary factors that affect the flowability of the final blend (or almost any powder), such as moisture content, particle shape/size/distribution, temperature/humidity and others, are discussed in more detail later in this chapter. Note that the measurement of flow properties and the design parameters they provide can also be applied to troubleshooting and developing corrective actions for flow problems in the preblending steps. 

Prior to beginning the discussion of the measurement of flow properties, it is beneficial to review how bulk solids are different than liquids. Since one of our primary concerns with bulk solids handling is flow, a term that is commonly associated with liquids, it is often assumed that the principles of fluid mechanics may be used to describe the behavior of... 

Measurement of Flow Properties at High Temperatures , ASTM D 3232,... 

The ease of deformation called plasticity characterizes the unvulcanized rubber compound, and causes the highly plastic rubber to flow easily. Viscosity is the resistance to plastic deformation or flow and, hence, the inverse of plasticity. Unvulcanized rubbers are not totally viscous but exhibit some elastic behavior. Rubber does not exhibit Newtonian flow as the shear rate is not proportional to the shear stress. Moreover, measurements of flow properties should be made at the shear rate of interest. 

Elementary Ideas of Flow Properties Flow Properties of Casting-slips Measurement of Flow Properties Dilatancy Rheopexy... 

Measurement of Flow Properties For the precise scientific measurement of viscosity and thixotropy in absolute units, see Rheology of Ceramic Systems . Here we shall restrict ourselves to a consideration of the torsion viscometer. 

The description, explanation, and measurement of flow properties of materials (for example of plastics) is the main object of the science of deformation and flowing of bodies known as rheology. ... 

Schwedes, J. Schulze, D. (1992) Letter to the editor Measurement of flow properties of solids. Bulk Solids Handling, 12(3), 454—455. 

Schwedes, J. and D. Schulze Measurement of Flow Properties of Bulk Solids, Powder Technol. 61(1990),59/68... 

---