Hydrodynamic Studies

Despite the fact that high-temperature and high-pressure operations are most often encountered in industrial EBRs, the lack of studies relevant to these conditions is notorious. Only some papers on high pressure/temperature hydrodynamics have been published by Jiang et al. (1992, 1997), Luo et al. (1997), Ruiz et al. (2005), and Sdnchez et al. (2008). It has been reported that pressure and temperature affect EBR hydrodynamics significantly by their effect on bubble behavior and liquid properties. 

Ruiz et al. (2005) studied the hydrodynamic characteristics of ebullated-bed systems operated at high pressure and temperature. The purpose of the work was to examine the effect of both variables on the hydrodynamic properties of ebullated-bed systems. The bed porosity and liquid minimum fluidization were measured and 

Because the effect of pressure on bubble behavior was not taken into account, correlations fail in the prediction of flow transition velocities at high pressures. A correlation was obtained by fitting experimental data published in the literature to an expression similar to that proposed by Zhang et al. (1997). The pressure range of the experimental data considered was from 5.6 to 15.6 MPa, being similar to those employed in EBRs for the hydroprocessing of heavy oil fractions. 

Modeling of Processes and Reactors for Upgrading of Heavy Petroleum 

FIG U RE 10.6 Experimental gas velocity to liquid velocity ratios from data reported in the literature and predicted values. ( ) Zhang correlation and ( ) Equation 10.3. (Adapted from Jiang, P. et al., Ind. Eng. Chem. Res. 31, 2322, 1992.) 

78-79), among others, called attention to the anomalous viscosity behavior of polymer solutions at very low concentration. Plots of j sp/C against C were found to curve either down or up at such concentrations, and the anomaly was attributed to the adsorption of polymer molecules onto the capillary wall. In order to calculate the thickness of the adsorbed polymer layer, Ohrn used the equation 

Rowland and Eirich81 estimated LH from the rates of flow through a sintered glass disc being in adsorption equilibrium with the polymer solution, using the relation 

Very recently, Gramain and Myard84 investigated the effect of the shear rate on LH, using high molecular weight fractions of polyacrylamide and polystyrene. Polyacrylamide was hydrolyzed to various degrees. Five commercial filters of pore radii from 1.5 to 6 fim were used as porous media. Measurements were carried out on polyacrylamide in water and polystyrene in toluene. 

Although the permeability reduction, which is defined as the ratio of flow rates before and after adsorption, was strongly affected by the nature of porous media, its dependence on the shear rate was similar for both polymers. A clear and reversible change of LH 

The measured values of LH appreciably increased with increasing shear rate, and those at the highest shear rate were 3-6 times as large as the diameter of a free polymer in the bulk solution. To explain this result Gramain and Myard considered that there should exist a net circulation of solvent in the adsorbed layer to elongate adsorbed polymers axially. This effect reduces the number of trains to about 3 or 4 per polymer chain. 

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Anxionnaz, Z., Cabassud, M., Gourdon, C., and Tochon, P. (2009) Hydrodynamic study and optimisation of the geometry of a heat exchanger/reactor. 2nd European Process Intensification Conference 2009, Venice. 

The application of Eqs. (17) requires a detailed knowledge of the two-phase hydrodynamics so that the parameters Ru Wc, U,a, U a, Vd, a, and Qt can be evaluated. The fluid dynamics of annular flows have been investigated experimentally. Russell and Lamb (R4) have studied the flow mechanism of horizontal annular flow Cousins et at. (C8) have dealt with droplet movement in vertical annular flow. Anderson and Russell (A6) have analyzed the interchange of droplets in horizontal systems, and numerous other hydrodynamic studies have been reported in Hewitt et al. (HI). Cichy et al. (C4) have reviewed the methods for evaluating the same hydrodynamic parameters that are also used in mass transfer studies. It is difficult to... 

Another survey by Ibl (13) in 1963 listed 13 mass-transfer correlations established by the limiting-current method, only four of which were derived from quantitative considerations. At the time of writing the total number of publications is more than 200. The majority of these concern flow conditions under which theoretical predictions are, at best, qualitative. More recently, an increasing number of publications deal with model hydrodynamic studies of more complex situations, for example, packed and fluidized beds. 

With the development of NMR-based experiments for studying folded proteins, structural analysis of denatured proteins entered a new phase (Wuthrich, 1994 Dobson et al., 1994 Shortle, 1996). Whereas other spectroscopies and hydrodynamic studies give data that correspond to a complex sum of the properties of all residues, NMR spectroscopy extracts information about individual residues. For the first time, local structural features could be directly inferred from the behavior of sets of residues along the sequence. 

Gamier, A., Chavarie, C., Andre, G., and Klvana, D., The Inverse Fluidization Airlift Bioreactor, Part I Hydrodynamic Studies, Chem. Eng. Comm., 98 31 (1990)... 

Source Adapted from various sources M. A. Elliot, Ed., Chemistry of Coal Utilization, 2nd Supplementary Volume, Wiley-Interscience, 1981 Cheremis-inoff, N, and P. Cheremisinoff, Hydrodynamics of Gas-Solid Fluidization, Gulf Publishing Co., 1984 Joaquin, R. H., Kinetic and Hydrodynamic Study of Waste Wood Pyrolysis for its Gasification in Fluidized Bed Reactor, European Foundation for Power Engineering, 2002 (http //www.efpe.org/papers.html). 

DOE, Slurry Reactor Hydrodynamics Studies Final Report, US Department of Commerce, National Technical Information Service, USA (DOE, 1985)... 

Since in a large diameter fluid bed, bubbles may bypass the catalyst, elaborate hydrodynamic studies are required to scale-up the reactor internals to accomplish the complete conversion of methanol. As mentioned earlier, essentially complete conversion of methanol is a process requirement otherwise, a costly distillation step must be added to recover unconverted methanol. 

The analysis of cutting planes normal to the main direction allows identification of local benzoic acid concentration (Kloeker et al., 2004). The velocity between the particles is relatively low, as shown in the hydrodynamic studies. This zone is thus almost stagnant, and diffusion becomes dominant resulting in a high concentration. Oppositely, for areas further away from the centre, the concentrations are low due to higher velocity. 

Various hydrodynamic studies of proteins, for example viscosimetry and diffusion, have shown that proteins behave in solution as fairly compact and symmetric particles. In time, equations were developed to describe the overall size and shape of proteins in terms of ellipsoids of revolution. Two basic types of ellipsoids of revolution, the prolate and oblate, are used to depict the approximate three-dimensional shapes of protein molecules. These are shown in Figure 4.12. Each ellipsoid of revolution may also be described by an axial ratio, that is, the ratio of the short axis to the long axis. A spherical protein molecule has an axial ratio of 1 1, whereas an asymmetric molecule, such as fibrinogen, may have an axial ratio of 1 10. 

In industry, many installations operate under pressure for technical and/or economic reasons. Although many hydrodynamic studies have been reported for liquid-gas contactors at atmospheric pressure, there are few concerning elevated pressure. The aim of this study is to investigate the influence of pressure on fluid flow in a packed column operating with a gas-liquid countercurrent. 

It has been shown by gel permeation chromatography (GPC) and NMR methods that cyclolinear structure of the backbone of synthesized polymers is obtained at the interaction of dichlororgano-cyclosiloxanea and dioxy-derivatives in the presence of HC1 acceptors only. The conclusion about cyclolinear structure of synthesized polymers is based on the data of hydrodynamic studies, MMD values and results of equilibrium rigidity determination. Cyclolinear structure of the backbone is also proved by NMR-spectroscopy method on 29Si nuclei. 

Previous hydrodynamic studies of trickle-beds are primarily experimental work involving pilot scale columns, for instance, constructing flow regime maps, and correlating pressure drop and liquid holdup data (1-5). Although these contributions have provided much insight, there is a lot of uncertainty in applying these data for industrial applications. 

These structures are also consistent with the results of hydrodynamic and scanning probe microscopy (SPM) studies reviewed by Shewry et al. (2003). Hydrodynamic studies indicate that the HMW subunits have an extended rod-like structure in... 

Of polypeptides with unusual chromophoric attributes, poly-L-tyrosine is the most thoroughly studied. X-ray and infrared evidence demonstrate that this polypeptide is a-helical in films cast from dimethyl formamide (Downie et al., 1959), and hydrodynamic studies have established that it exists as a helix in solution as well (Coombes et al., 1960). The helical form, which is stable in both dimethyl formamide and aqueous solution of pH 10.85, may be transformed into the random coil either by increasing the... 

R. Raju and S. Roy, "Hydrodynamic Study of High Speed Flow and Heat Transfer through a MicroChannel. Journal of Thermophysics and Heat Transfer, 19.1 (2005), pp. 106-113. 

A. Hydrodynamic Studies with an Internally Finned Tube... 

Hydrodynamic Studies of Microbial Adhesion and Passage of Bacteria through Membranes..331... 

C. Deslouis and B. Tribollet, "Flow Modulation Technique and EHD Impedance A Tool for Electrode Processes and Hydrodynamic Studies," Electrochimica Acta, 35 (1990) 1637-1648. 

Hydrodynamic studies in the coaxial mixer without solid particles... 

In view of taking part into a hydrodynamical study of this groundwater trapped below a confining bed, we have carried out an isotopic study of the tritium, radiocarbon, and deuterium contents in about forty deep... 

H. Belfort and G. Guter. Hydrodynamic Studies far Electrodiaiysis, Office of Saline Water... 

The hydrodynamic study at a mesoscopic scale requires the understanding of instantaneous local solids flow structure. The time-variant flow behavior is complex. Analyses of the instantaneous flow structure require recognizing the following factors. 

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