Penetration capillary

In Section 6.1 we discussed the rise of a liquid in a capillary of which the inner wall is well wetted. In vertical position the rise is compensated by the hydrostatic pressure, as expressed in Equation 6.6. For a horizontally positioned capillary, the liquid 

FIGURE 8.9 Displacement of a liquid by another liquid in a capillary. 

The driving force for the displacement is the capillary pressure (see Section 6.1)  

When air is taken for L2, for which ii 0, 2 is given by PoiseuiUe s equation  

It is inferred from Equation 8.20 that, for a given capillary, the velocity of penetration of the one liquid into the capillary, thereby displacing the other liquid (or air) is enhanced by lower values of r, a high value of y, and a small value of 0(cos 0 — 1). The last two conditions, high y and small 0, are usually not compatible. 

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Capillary pressure gradients and Marongoni flow induce flow in porous media comprising glass beads or sand particles [40-42], Wetting and spreading processes are an important consideration in the development of inkjet inks and paper or transparency media [43] see the article by Marmur [44] for analysis of capillary penetration in this context. 

The consequences of the wetting ridge in the capillary penetration of a liquid into a small-diameter tube have been evaluated. Viscoelastic braking reduces the liquid flow rate when viscoelastic dissipation outweighs the viscous drag resulting from Poiseuille flow. 

The vasculature is established by the 18th day of gestation in rats, and comes from the arterial supply as the anterior cerebral vessel, eventually entering the basal lamina via septal tributaries of the olfactory artery (Szabo, 1988). Unlike the MOE, the organ s capillaries penetrate in loops into the neuroepithelium. Blood from the vomeronasal complex arrives for collection in the vomeronasal vein, as described earlier [Fig. 2.11(a)]. The establishment of the highly vascular columnar complexes seen in the ophidian organ has not been correlated with functional development (c.f. Wang and Halpem, 1980 Holtzman and Halpem, 1990). 

A highly complex network of arteries, arterioles, and capillaries penetrates the dermis from below and extends up to the surface of, but not actually into, the epidermis. A matching venous system siphons the blood and returns it to the central circulation. Blood flow through the vasculature is linked to the production and movement of lymph through a complementary dermal lymphatic system. The dermis is laced with tactile, thermal, and pain sensors. 

Inert polymer matrices, studied for use in possible controlled release applications, have used porosimetry to investigate a number of properties [54-56]. The kinetics of liquid capillary penetration into these matrices was explored using a modified Washburn equation [54]. It was shown that water... 

In many applications, powders come into contact with a liquid and we would like to quantify their wetting behavior. The usual way to do this is by the capillary rise method [233,234], In a capillary rise measurement the powder is pressed into a tube of typically 1 cm diameter (Fig. 7.7). This porous material is then treated as a bundle of thin capillaries with a certain effective radius [235-237], In order to measure this effective radius, first a completely wetting liquid is used. Either the speed of the liquid rise is measured (this technique is sometimes referred to as the capillary penetration technique [238]) or the pressure required to keep the liquid out of the porous material, is determined. This backpressure is equal to the... 

Figure 2.19 Mesoporous nanocompaitment films and stimuli-fiee, automodulated stepwise release of materials based on the nonequilibrated rates between evaporation and capillary penetration.108 (Reprinted with permission from Q. Ji et al., J. Am. Chem. Soc. 2008,130, 2376-2377. Copyright 2008 American Chemical Society.)...

Excess starch dispersion is drained from the ends of the nip. The surface size is transferred to paper by capillary penetration, pressure penetration and by hydrodynamic force during nip passage. 

Capillary penetration experiments. Using a series of nonpolar and polar probe liquids, the solid surface tension of unmodified and modified particles was evaluated by capillary penetration experiments [35,36], The strategy is based on a modified Washburn equation ... 

Acknowledgement Authors thank Dr. M. Motomov for providing assistance in grafting of particles, Ms. G. Adam, Ms. G. Zedler and Mr. U. Streller for FTIR-ATR, capillary penetration and SEM investigations, respectively. 

It thus appears that the adjuvant effect of surface-active agents on herbicidal activity can be explained in terms of the surface-chemical interactions between the droplet of herbicide solution and the plant-leaf surface. Although, as we have seen, capillary penetration is one aspect of... 

Figure 10.2 showed the predicted capillary penetration by some liquid metals which were assumed to wet perfectly. The predictions for all the systems suggest that both horizontal and vertical 0.1 mm wide braze gaps will be filled to a depth of 10 mm, a typical braze depth, in much less than 1 second. 

Many different techniques have been developed for the measurement of contact angles 17.8). Of these, the three most useful methods are the Wilhelnty technique, the technique of capillary rise at a vertical plate, and the drop shape methods. These techniques require the solid surface to be flat and smooth. Direct measurement of contact angles on fibers (of uniform thickness) can also be performed using the Wilhelmy technique. For nonflat surfaces or particles, indirect methods such as capillary penetration into columns of powders, sedi-... 

The measurement of contact angles on solids in powder or particle form is a challenging task, and numerous methods have been proposed 7. In this section, three successful indirect approaches are discussed capillary penetration into columns of powders, sedimentation volume of particles, and solidification fronts of particles. These methods are indirect because they provide the solid surface tension rather than the contact angle. For the sake of completeness, various direct approaches are also summarized briefly. 

One method, therefore, is to measure the pressure necessary just to balance the Laplace pressure, which drives liquid into a capillary bed. i.e.. the limiting pressure necessary to prevent capillary penetration ... 

Groszek and Witheridge showed that such oleophilic powders are highly effective in increasing load-carrying capacity. They provided some evidence that the effectiveness is due to the fact that oleophilic particles preferentially attach to bearing surfaces in a basal plane orientation. In that orientation the molybdenum disulphide would provide less opportunity for capillary penetration, and would be less susceptible to chemical reactions. 

II. 1.6b. Phenomena involving capillary penetration will be discussed in sec. 5.9 they are very relevant for a number of industrial processes. In fact, several techniques yield y cos a rather than / the trend is that / is more easily measured than cos a. 

In two respects capillary penetration (or depression) does give rise to independ-... 

Droplet Droplet Binder formation coalescence dispersion overlap by wetting capillary penetration... 

FIG. 21-101 Influence of capillary penetration on drum granule size. Increasing penetration rate increases granule size and decreases asymmetry of the granule-size distribution. [After Gluba et al.. Powder Hand. Proc., 2, 323 (1990).]... 

Desai TR, et al. Determination of surface free energy of interactive dry powder liposome formulations using capillary penetration technique. Colloids Surf B Biointerfaces 22(2) 107-113, 2001. 

The Lucas-Washbum equation is the simplest equation to model the rate of capillary penetration into a porous material. It is derived from Poiseuille s iaw (4) for laminar flow of a Newtonian liquid through capillaries of circular cross-section by assuming that the pressure drop (AP) across the liquid-vapor interface is given by the Laplace-Young (6) equation. In practice, depending... 

Bubble Point Pressure Test Membrane filters have discrete pores or capillaries penetrating from one side of the membrane to the other. When a membrane has been completely wetted, Squid is held in these capillary pores by surface tension. The Bubble Point of a membrane is defined as the minimum gas pressure required to break this surface tension and force the liquid out of the capillaries. Bubble point is a measure of relative pore size. 

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