Radial liquid spreading coefficients

Berner and Zuiderweg [112] obtained the following equaticm for determination of the coefficient of radial liquid spreading for Raschig rings and Intalox saddles... 

Hoek [86] proposed a radial spreading coefficient to characterize the liquid distribution. This coefficient is a measure of how quickly a packing can spread a vertical liquid stream radially as the liquid progresses down the column [86]. Radial mixing tends to reduce the effects of... 

Many studies are available dealing with radial spreading from single points or other geometries (Hoftyzer, I96U Onda et al., 1973 Herskowitz et al., 1979). In these studies, the liquid spreading is supposed to be ruled by some diffusional mechanism, which leads to write a diffusion-like equation introducing a radial spread coefficient Dp ... 

Increasing of tiie radial spread coefficient of the liquid diase in the apparatus cross-section. It is due to the increased ratio of the liquid trickles deviation in horizontal direction to the he ht at which this vialirm takes place, equal to the height of a packing lamella [243], The problem is discussed... 

D- coefficient of radial spreading of liquid, called also liquid spread facter, m h- hei of the packing, current coordinate, m. 

Besides the coefficient of radial spreading, to characterize the liquid spreading, the distribution width is introduced [142]. This value is connected with a modified Gaussian distribution function and can be obtained also experimentally. 

A common equation for determination of the radial spreading coefficient can be obtained in case of statistical consideration of the moving of the liquid streams in the irrigated column. Making such considerations Tour and Lerman [57] have worked out the equation ... 

The data show that at low value of the liquid flow rate the radial spreading coefficient is not depending on it. After a given flow rate its... 

Fig. 13. Influence of the liquid superficial velodly on llie lupnd radial spreading coefficient for Holpack packings. Tfac numbers of the lines are explained in Table 33, Chapter 3. The line P is for randon Rasdbig tings 30x30x3 nun.

Fig. 14. Comparison between the experimental data for the liquid radial spreading coefficient for some packings presented in Table 3 and the line calculated by Eq. (18).

Taking into account that the flow distribution is a statistical phenomenon, the distribution of the liquid and phases should be calculated using one and the same differential equation which is Eq. (8-3) of Cihla and Schmidt [6]. The only difference in their distribution is connected with the feet that the motion of the liquid phase is due to the gravity force, and the motion of the gas phase - due to the pressure drop. That is y for one and the same packing, the radial spreading coefficients D for each phase are not equal, and there is no reason to expect them to be equal. 

D- coeffici of liquid radial spreading (liquid spreading ctor), m ... 

D. DdionovarAtanasova, N. Kolev, S. Nakov, Radial spreading coefficient of dm liquid phase for some higly effective random paddmgs. (Ready for publication). 

The problem to be solved in this paragraph is to determine the rate of spread of the chromatogram under the following conditions. The gas and liquid phases flow in the annular space between two coaxial cylinders of radii ro and r2, the interface being a cylinder with the same axis and radius rx (0 r0 < r < r2). Both phases may be in motion with linear velocity a function of radial distance from the axis, r, and the solute diffuses in both phases with a diffusion coefficient which may also be a function of r. At equilibrium the concentration of solute in the liquid, c2, is a constant multiple of that in the gas, ci(c2 = acj) and at any instant the rate of transfer across the interface is proportional to the distance from equilibrium there, i.e. the value of (c2 - aci). The dispersion of the solute is due to three processes (i) the combined effect of diffusion and convection in the gas phase, (ii) the finite rate of transfer at the interface, (iii) the combined effect of diffusion and convection in the liquid phase. In what follows the equations will often be in sets of five, labelled (a),..., (e) the differential equations expression the three processes (i), (ii) (iii) above are always (b), (c) and (d), respectively equations (a) and (e) represent the condition that there is no flow over the boundaries at r = r0 and r = r2. 

Determination of the coefficient of radial spreading of the liquid phase The coefficient of radial spreading of the liquid phase defced by Eq. (3) depends on the poking type and dimensions and in many cases on the hydrodynamics of the liquid ph e too. The investigations of Stanek and Kolev [S], carried out with random packings show, that it is not crmstant over the whole cross-section of the apparatus. The ane result is obteined also by Marchot et al. [89]... 

The coefficient of radial spreading of liquid phase is usually determined using the method described by Kabakov and Oilman [SS]. The method is based on the solution of Eq. (3) for a single irrigating jet orientated in the centre of the cross-section of the colunm. The solution is as follows ... 

To ensure uniform distribution over the column cross-section between the liquid distributor and the main honeycomb packing, a special redistribution layer of inclined Raschig rings is mounted. For this layer the packing No 4, Table 7, Chapter 8, with an average coefficient of radial spreading ZN2.64.10 m is chosen. As shown in Chapter 8, part 8.3.4., at the time of the column construction, this packing ensured minimal pressure drop. 

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