Flow regime dilute

Figure 20 Predicted flow regime diagram of the industrial MIP reactor, with solids flux as a function of the imposed total pressure drop at fixed gas flow rate. The snapshots of voidage profile refer to the transition, from left to right, the dilute transport, choking transition in between with different solids inventory, to the dense fluidization (Lu et al., 2007).

Pneumatic conveying systems can be classified on the basis of the angle of inclination of pipelines, operational modes (i.e., negative- or positive-pressure operation), and flow characteristics (i.e., dilute or dense phase transport steady or unsteady transport). A practical pneumatic conveying system is often composed of several vertical, horizontal, and inclined pipelines. Multiple flow regimes may coexist in a given operational system. 

Figure 11.2. Flow regimes for horizontal conveying of solids (a) Dilute suspension flow ...

Figure 4. Approximate dependency of flow regime on gas velocity and column diameter (water and dilute aqueous solutions), from Shah et al. [36].

High mass-transport coefficients are obtained in cells with a rotating cylinder electrode (RCE) and a small gap between the anode and the cathode, Fig. 4(a). High rates of mass transport are experienced in the turbulent flow regime, so that RCE reactors allow metal deposition at high speed, even from dilute solutions. RCE reactors have been operated at a scale involving diameters from 5 to 100 cm, with rotation speeds from 100 to 1500 rpm and currents from 1 A to 10 kA [79], It... 

The first term on the RHS in the viscosity closure denotes the kinetic contribution and dominates in the dilute regime. The second term on the RHS denotes the collisional contribution and dominates in the dense flow regime. 

Lean phase fluidization As the gas flow rate increases beyond the point corresponding to the disappearance of bubbles, a drastic increase in the entrainment rate of the particles occurs such that a continuous feeding of particles into the fluidized bed is required to maintain a steady solid flow. Fluidization at this state, in contrast to dense-phase fluidization, is generally denoted lean phase fluidization. Lean phase fluidization encompasses two flow regimes, these are the fast fluidization and dilute transport regimes. 

However, it is not always easy to distinguish between the flow behavior encountered in the fast fluidization and the transport bed reactors [56]. The transport reactors are sometimes called dilute riser (transport) reactors because they are operated at very low solids mass fluxes. The dense riser transport reactors are operated in the fast fluidization regime with higher solids mass fluxes. The transition between these two flow regimes appears to be gradual rather than abrupt. However, fast fluidization generally applies to a higher overall suspension density (typically 2 to 15% by volume solids) and to a situation wherein the flow continues to develop over virtually the entire... 

Flow regime Bubbling, slugging or turbulent, distinct upper interface Fast fluidization Dilute transport... 

For gas-particle flows, fhe mosf obvious manifestation of non-equilibrium behavior is particle trajectory crossing (PTC) at KUp = oo (i.e. no collisions). PTC occurs in the very-dilute-flow regime ( p c 1) and is most easily identified when fhe granular femper-afure is null (Map = c ). An example of PTC is shown in Figure 1.4. The panel on fhe... 

Tubular Precipitator. This type of continuous operation may be employed to reduce polydispersity of precipitates (Raphael et al. 1997 Raphael and Rohani 1999). The tubular precipitator may operate either under the turbulent flow or laminar flow regime. The reactants are added into the inlet section equipped with static mixers and may also enter as a multi-port feed along the length of the tubular precipitator. If the reactant feeding streams are too concentrated or if too excessive formation of precipitate occurs in the inlet section of the precipitator, a third stream of solvent is also fed to dilute the flowing suspension. The latter may contain a protective colloid or surfactant that prevent agglomeration of precipitate. 

Fig. 1 Flow regimes in De-Re space for dilute aqueous PEO solutions through microlength-scale contraction geometries [4]...

Understanding how the sample zone interacts with the surrounding solution is of the utmost importance for system design and method implementation. In this regard, the flow regime - also alterations in flow pattern due to implementation of different strategies -and sample dispersion/dilution are key aspects to be considered. 

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