Classification of fluids

According to rheology, which embraces the study of flow behavior in very general way, there are two main types of flow viscous and elastic. The first 

A wide variety of nonlinear relationships between stress and shear rate have been used. Possibly, the most common one known as the power-law, also appearing in Table 10.1, representing the shear thickening and shear thinning fluids as described there. If the exponent n is less than one, the material flows more easily the faster it is sheared, and the apparent viscosity 

Newtonian II. Non-Newtonian 1. Time independent x = ry Air, water, steam, all gases, milk, vegetable oil, honey 

Viscoelastics No unique Saliva, nearly aU-biological fluids, concentrated tomato soup, bread dough, many polymeric solutions 

Definition of viscosity x = shear stress v = fluid velocity Av/Ay = Y (shear rate). 

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Classification of Fluid Services The code apphes to piping systems as illustrated in Fig. 10-124, but two categories of fluia services are segregated for specif consideration as follows ... 

Figure 25 The classification of fluid-solid systems with respect to bed expansion as function of air velocity [36]...

Table XIV Hazard classification of fluids according to their MESG1 and/or MIC2 values. (Extract from European Standard EN 50.014)...

D. Recent Developments in the Engineering Classification of Fluid Behavior 88... 

In this section we will discuss the phase behaviour of binary systems. In 2.2.2.1 the classification of fluid phase behaviour according to van Konynenburg and Scott [5] is discussed. The occurrence of solid phases introduces an extra complication in binary phase phase diagrams. This is discussed in 2.2.2.2. 

Many reactors fall in the classification of fluid-solid catalytic units where the catalyst may be retained in a fixed-bed position in the reactor with the reactant flowing through the catalyst bed, or the unit may be operated as a fluidized-bed reactor with the catalyst particles being suspended in the flowing fluid due to motion of the fluid. A third type of reactor is one in which the catalyst particles fall slowly through the fluid by gravity in the form of a so-called moving bed. 

This chapter presents a brief review of the rheological classification of fluids and instruments used for viscosity measurements. A discussion of the rheology of suspensions and how it relates to that of emulsions is given. Predictive correlations for emulsion viscosity are discussed in detail. The effect of added solids to an emulsion is fully treated, and its relation to a bimodel system is discussed. 

The range of intermolecular interactions was recognized as an important factor already a long time ago and was used for instance, along with other quantities, in a classification of fluids by Andersen [6] but a systematic investi-... 

Simple classifications of fluids can be made on the basis of their rheological profiles. Figure 3.78 shows the (a) shear stress and (b) viscosity profiles for various systems. From Figure 3.78 one may define the following systems. Newtonian systems have a constant viscosity with respect to shear rate. Dilatant (or shear-thickening) systems have a viscosity that increases with respect to shear rate. Pseudo-plastic (or shear-thinning) systems have a viscosity that decreases with respect to shear rate. Yield-stress materials are materials that have an initial structure that requires a finite stress before deformation can occur. The stress that initiates deformation is defined as the yield stress. 

Figure 3.79. Classification of fluids on the basis of the time dependence of shear viscosity.

This classification of fluids is essentially the same as that of Skelland [4],... 

Using the information just given, the overall kinetics of the PTC cycle in a two-phase system can be determined. Considering the complexity of the systems, several approaches to LLPTC modeling have been taken (Evans and Palmer, 1981 Lele et al., 1983 Chen et al., 1991 Wu, 1993, 1996 Bhattacharya, 1996). All these are based essentially on the classification of fluid-fluid reactions into four regimes, as described in Chapters 14 and 15. 

Fig. 4 shows schematic pTx diagrams (upper row) and the corresponding p T) projections (lower row) for a binary system here p = total pressure, T = temperature, x = mole fraction. Most important for the classification of fluid phase equilibria is the shape of the different critical curves. A critical curve connects all binary critical points in the pTx space here the two coexisting fluid phases become identical, namely at the extreme values of the isothermal p x) or isobaric T x) sections. Details can be found in the earlier publications [2-6,10,12]. 

FIGU RE 17.6 Rheological classification of fluids showing (a) Newtonian, (b) non-Newtonian,... 

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