Fluid flow behavior

The micro channel structure of the device is fabricated in a glass wafer by common procedures (Figure 4.14). To allow sealing of the channels, the whole surface is coated with CYTOP, a Teflon -like polymer. On the one hand it forms a bondable layer and on the other it makes the micro channel surface strongly hydrophopic. Bonding with a CYTOP-coated cover glass plate occurs under moderate pressure at 180 °C. Because sometimes the CYTOP layer peels off and disturbs the fluid flow behavior, the whole device is fabricated in polydimethylsiloxane (PDMS) [71]. 

Our approach to the problem of predicting the performance of fluidized bed filters involves logically coupling models that describe the flow behavior of the fluidized state with models that describe the mechanisms of particle collection. The collection mechanisms analysis leads to expressions for determining the collection efficiency of a single filter element. An example of a collection mechanism is inertial impaction by which a particle deviates from the gas stream lines, due to its mass, and strikes a collector. It should be noted that because particle collection mechanisms are functions of the fluid flow behavior in the vicinity of a collector, there exists an interdependency between fluidization mechanics and particle collection mechanisms. 

The major types of fluid flow behavior can be described by means of basic shear diagram of shear rate versus shear stress, such as Figures 1-2 and 1-3. In Figure 1-2, the shear stresses are plotted against the shear rates (independent variable) which is the conventional method. However, some authors plot shear rates against the shear stresses (independent variable) as shown in Figure 1-3. With the introduction of controlled-stress rheometers, the use of shear stress as the independent variable is often desirable. 

Crowe D. E., Riciputi L. R., Bezenek S., and Ignatiev A. (2001) Oxygen isotope and trace element zoning in hydrothermal garnets windows into large-scale fluid-flow behavior. Geology 29, 479-482. 

This produces gradual pressure and density differences around the object which result in a certain kind of fluid flow behavior. However, when the Mach number is greater than 1, the object is moving faster than the speed of sound. When this happens the pressure disturbances cannot move out of the way fast enough, and very abrupt density and pressure changes, known as shock waves, appear. This results in a very different fluid flow behavior. These shock waves are the cause of the sonic boom sometimes heard when an airplane exceeds the speed of sound. 

Melton and Malone (44, 45) developed an expression for turbulent flow of a non-Newtonian fluid through tubulars that was modeled after the Bowen relationship. Reidenbach et al. (11) modified the relationship to account for the changing density of foam as it travels through the tubulars. Equation 28 was developed for non-Newtonian fluids however parameters were developed to account for Newtonian fluid flow behavior. Table V shows the parameters for water. 

The heat transfer characteristics in multiphase systems depend strongly on the hydrodynamics, which vary significantly with particle properties. The particle size, size distribution, and shape affect the particle and fluid flow behavior through particle-fluid and particle-particle interactions. A discussion of the hydrodynamic characteristics of packed and fluidized beds follows. 

Equation 20 shows that a porous medium is permeative, that is, a shear factor exists to account for the microscopic momentum loss. Our preliminary study recently reveals that, however, a porous medium is not only permeative but dispersive as well. The dispersivity of a porous medium has been traditionally characterized through heat transfer (in a single- or multifluid flow) and mass transfer (in a multifluid flow) studies. For an isothermal single-fluid flow, the dispersivity of a porous medium is characterized by a flow strength and a porous medium property-de-pendent apparent viscosity. For simplicity, we discuss the single-fluid flow behavior in this chapter without considering the dispersivity of the porous medium. 

Kinematic similarity is the similarity of fluid flow behavior in terms of time within the similar geometries. Kinematic similarity requires that the motion of fluids of both the scale model and prototype undergo similar rate of change (velocity, acceleration, etc.). This similarity criterion ensures that streamlines in both the scale model and prototype are geometrically similar and spatial distributions of velocity are also similar. 

One of the advantages of physical modeling is the direct measurements and observation of the fluid flow behavior inside the scale model that represent a prototype s field operation. Typical flow measurements include velocity, pressure, and temperature. In some cases, species monitoring is also used to assess mixing performance of the scale model. 

Stroud,C.,Branch,M.C.,Vian,T.,Sullivan, N.,Strobel, M., and Ulsh, M. "Characterization of the Thermal and Fluid Flow Behavior of Industrial Ribbon Burners." Fuel 87 (2008) 2201-10. 

Turan R B and Okur A (2013), Prediction of the in-plane and through-plane fluid flow behavior of woven fabrics . Text Res J, 83(7), 700-717. 

As we shall see in Section 5.1.1.1, reactors can be classified as batch and continuous reactors, which in turn can be idealized as stirred-tank and plug-flow reactors. We shall not consider any nonideality of fluid flow behavior, since most industrial reactors exhibit only small deviations from ideality. One object of reactor design and operation is to ensure this. 

CFD analysis computes local fluid velocity, pressure, and temperature throughout the region of interest for problems with complex geometries and boundary conditions. By coupling the CFD-predicted fluid flow behavior with the electrochemistry and accompanying thermodynamics, detailed predictions are possible. Improved knowledge of temperature and flow conditions at all points in the fuel cell lead to improved design and performance of the unit. 

The subjects in this chapter will include fluid statics, fluid flow phenomena, categories of fluid flow behavior, the equations of change relating the momentum transport, and the macroscopic approach to fluid flow. 

Take a look at Fig. 48.7. This should give you an idea of some of the variations of fluid flow behavior. The gradients or slopes of these lines or curves are variable within the identified flow regime. It is whether or not the curves pass through "the origin" and the general shap>e of the curve that defines the type of behavior. 

Figure 48.7 Examples of variations of fluid flow behavior.

Figure 2.9 Schematic of transient fluid flow behavior inside a channel. For times t < 0 the flow is in steady-state, due to the over-pressure AP applied to the left. The flow profile is a characteristic parabola. Suddenly, the pressure AP is turned off at f = 0. However, the inertia keeps up the flow. For t > 0 the fluid velocity diminishes due to viscous friction, and in the limit t oo the fluid comes to rest relative to the channel walls...

Since suspensions, or slurries, have not been used in either of the homogeneous reactors built by ORNL, the slurry equipment problems have received less attention than corresponding solution problems. Much of the solution technology can be applied to slurries, although additional difficidties such as the settling tendency of slurries, their less ideal fluid-flow behavior, and their erosiveness must be taken into consideration. 

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