Redistribution of liquid

Packed columns must be provided with good initial distribution of liquid across the column cross section and redistribution of liquid at various height intei vals that decrease with increasing column diameter. A wide variety of distributors and redistributors are available. Packed columns should be considered when ... 

Ov Crall, the careful design of a distributor for liquid in the top of a packed tower, and for the redistribution of liquid flowing dow n multi-section packing in the tower, is essential to good consistent tower performance. However, the liquid flow is not alone, the uniformity of vapor distribution is likewise essential, because non-uniform vapor distribution can cause non-uniform liquid downflow. Then, there is the selection of the packing itself and its characteristics and requirements/sensitivity to the uniform distribution of the liquid and vapor. As earlier emphasized, the level of the distributor tray or trough can be critical to the consistent uniform liquid distribution. 

The assembly shown in Fig. 2.104 illustrates a set-up for simple fractionation using a Vigreux column which has moderate fractionating efficiency and is probably one of the most widely used columns. The column consists of a glass tube with a series of indentations such that alternate sets of indentations point downwards at an angle of 45° in order to promote the redistribution of liquid from the walls to the centre of the column. The mixture to be fractionated is placed in a flask of convenient size (it should be one-third to one-half full), a few fragments of porous porcelain added and a water condenser attached to the side-arm. The distillate is collected in small flasks or in test tubes. The bulb of the thermometer... 

In cocurrent downflow the liquid distribution is the most sensitive part, since there is no redistribution of liquid within the monolith. The liquid must be equally distributed to every channel at the top. On the other hand, when the liquid is evenly distributed, there is no maldistribution further down in the monolith. Nonuniform liquid distribution gives nonuniform conversion, resulting in larger reactors and lower selectivities. 

Syneresis. The most actual problem in the study of foam systems is the spatial redistribution of liquid phase under the action of external fields and internal inhomogeneities. 

To calculate unsaturated hydraulic conductivity A"(p) we have to take into consideration the spontaneous filling (snap-off) of the slit and the central pore for imbibition and the spontaneous redistribution of liquid for drainage. These aspects are extensively discussed in Film Adsorption on Rat Surfaces and in Slit-Shaped Pores and Capillarity and Pore Shape . The unsaturated conductivity before slit filling is given as ... 

Excellent initial liquid flow distribution is imperative. Poor redistribution of liquid. 

This is akin to a vertical radiator heating a room. Warm air near the radiator starts rising and generates turbulent flows. Similar turbulent flows exist in a soap film near the lateral walls. These flows close the loop at the center (Figure 8.15). Thus, there is a net redistribution of liquid from the central portion of the film toward the bottom. The physical law s involved are rather complex. For more details, the reader is encouraged to consult the book by Mysels, Shinoda, and Frankel/ ... 

Equation (61) is the conservation equation for the liquid in which the quantities and pB can be expressed in terms of Pp, ApXp, andR using Eqs. (45) (46) (47). It is to be noted that Eq. (61) is valid whether coalescence occurs or not. Coalescence occurring in a volume element does not, by itself, change the amount of liquid in the element. It only causes a redistribution of liquid from the ruptured films and Plateau border channels to the remaining Plateau border channels within the element. The change in the amount of liquid in the element occurs only due to drainage. The eflfect of coalescence is felt through R. When coalescence occurs, the local R increases. The two boundary conditions required for Eq. (61) are presented next. 

Since the condition of uniform curvature has to be satisfied in each liquid cluster separately, a cluster labeling routine based on the Hoshen-Kopetman algorithm [8] has been implemented. During the redistribution of liquid, clusters may split or merge, so that periodic re-labeling is necessary. In this way, topological changes in the liquid phase are conveniently handled. 

The collector-distributor VS, designed by Sulzer Conii ny [11], presented in Fig. 72, is a compact construction. It is used whenev )llection and redistribution of liquid is required at very height liquid l( ds. 

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