Radial heterogeneity

There are several ways to deal with this problem. The simplest in concept is to use liquid imbibed particles that are uniform in structure, such as sugar cubes [12, 13] as already mentioned above. To my knowledge, this has never been done for structure studies. The second is to use NMR-invisible particles, for example, glass, and fill the spaces between the particles with a liquid such as water that can be imaged. The third is to use the usual radially heterogeneous particles and then use software to calculate the parameters. One first determines the centers of each particle and then decides whether the particles are in contact with each other or not by the distances between the centers [14]. 

From these diagrams, it can be seen that gas velocity in the fast fluidized bed diminishes along the radial direction from the center to the wall. Local gas velocities in the center are much higher than the corresponding superficial gas velocities, and radial heterogeneity of gas velocity increases with increase in superficial gas velocity and solids circulation rate. The local gas velocity can be estimated by using the following equations ... 

Wall effect gives rise to radial heterogeneity. Although Soo (1989), Ding et al. (1992) and Ding and Gidaspow (1990) proposed boundary conditions for their models, it is still considered necessary to measure relevant parameters near the wall, such as fluid velocity, particle velocity, and void fraction. Inlet and outlet effects are even more difficult to generalize, and will therefore be discussed only in a qualitative sense. 

For considering radial heterogeneity in a two-phase system, the pseudo-fluid model is simultaneously applied to the core dilute region and the wall dense region, resulting in the so-called two-channel model (Nakamura and Capes, 1973 Bai et al., 1988 Yang, 1988 Ishii et al., 1989 Berruti, 1989 Rhodes, 1990). 

Radial heterogeneity, showing a dilute core region surrounded by a dense annular region next to the wall, is attributed to the role of the wall in... 

Model LG applies just as well to radial heterogeneity, though in a somewhat different functional form, to describe the fluid dynamics at any radial position r ... 

In order to calculate Ug(r) and Ud r) from the specified operating parameters Ug and Gs, it is necessary to know the dominant factor defining radial heterogeneity. Extending the energy minimization method to overall hydrodynamics, a stable radial profile calls for not only Model LR for local hydrodynamics at every point, but also the minimization of the cross-sectional average Nst for overall stability, which is defined by... 

Therefore, for coal burning, neglecting radial gas dispersion and radial heterogeneity of solids concentration might be acceptable. Gas-solid flow can thus be simplified to a one-dimensional model with axial distributions only. 

Temperature This criterion is often underconsidered in the operation of a preparative chromatographic process. Temperature has a direct impact on the adsorption isotherms and modifies the retention of the separated compounds. A significant loss of efficiency can be observed with a radial heterogeneity of the temperature, which will modify the retention of the products. This heterogeneity is linked to a difference between the temperature of the eluent and the temperature of the column body. This is particularly important to consider on small-scale preparative devices (5-10 cm ID columns), the wall effect is less significant for larger columns. 

The reference CAPRA oxide core is characterised by high Pu concaitration, and by radial heterogeneity. Hie reactor physics calculation methods for such cores have been examined and a calculation route using the ERANOS code system has been set up. 

ZPPR-1 IA,I IB Radially heterogeneous reactors prototypic of a Westinghouse reactor design. They have a central blanket and three fuel rings separated by blanket zones. Twenty-four sodium-filled CRPs will be present. The core fuel volume fraction of 0.39 in IIA will be reduced to 0 32 in I IB. Criticality of li A is expected in November 1979. 

ZPPR-11C,1 iD Radially heterogeneous reactors with cylindrical boundaries. These systems have central blankets, and two fuel rings separated by a blanket ring. The blanket ring thick- ness is I6S mm in 11C and will increase to 330 mm in 1 ID. The program is expected to be completed in February 1981. 

The investigated active carbons have both the porous structure and the nature of surface var5nng within the particles (see Figures 4 and 5). The AG active carbon, of the greatest differentiation of textural and surface hydrophilic character was used for the estimation of the effect of radial heterogeneity on the properties of impregnated active carbon. For this reason, the initial carbon was impregnated and subsequently abraded in the spouted bed, so as to study the structural and protective properties of the obtained samples [54]. 

Fuel enrichment (TRU/HM) Reference core design radially heterogeneous core... 

The STAR-H2 reactor uses a radially heterogeneous core layout of ductless assemblies. The pin lattice is open with a large coolant volume fraction. 

The radially heterogeneous core layout (i.e. with fertile material blanket assemblies interspersed in the core itself) is used to flatten radial power profile and to enhance internal breeding so as to reduce bum-up reactivity loss. 

Titanium isotopes and the radial heterogeneity of the solar system. Earth Planet. Sd. Lett., 266, 233-244. 

In the theory of free oscillations of the earth it is assumed that the earth is a spherically symmetric elastic body. Takeuchi and Saito obtained the normal modes for the radially heterogeneous earth. Two Independent modes are identified toroidal modes, corresponding to a twisting motion of the sphere (SM waves), and spheroidal modes, corresponding to a distorting motion of the sphere (P-SV waves). Once the normal modes are obtained, the motions of the earth can be expressed by the weighted superposition of all normal modes. 

Figure 5.1 Typical homogeneous and heterogeneous sodium-cooled fast reactor core configurations (a) homogeneous core, (h) axial heterogeneous core, and (c) radial heterogeneous core. All rights reserved hy Japan Atomic Energy Agency.

Figiue 7.28 [1] compares radial power distributions with ordinary blanket fuel rods or thick walled duct tubes in the outer region of blanket assemblies. Simplified R-Z calculations for radial heterogeneous cores are used to clarify the effect of the duct tubes. The relative power peak near the seed and blanket interface is significantly reduced by replacing the blanket fuel rods with the duct tubes. 

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