Thinning capillary liquid

The mechanism is essentially a combination of the deformation of a round liquid jet by aerodynamic forces and the instability of the deformed jet. The liquid jet is first accelerated rapidly in the high speed air stream (Fig. 3.3b). The jet diameter is thus significantly reduced as it interacts with the surrounding air stream. The direction of the thinning capillary liquid jet is influenced by the interaction between the liquid jet and the turbulent structures of the surrounding air stream. The formation of... 

The second mechanism can be explained by the wall liquid film flow from one meniscus to another. Thin adsorptive liquid layer exists on the surface of capillary channel. The larger is a curvature of a film, the smaller is a pressure in a liquid under the corresponding part of its film. A curvature is increasing in top s direction. Therefore a pressure drop and flow s velocity are directed to the top. 

In filled thermometers the thermal expansion of a gas or a liquid is transmitted through a thin capillary tube to a bellows or helix, where the deformation indicates the temperature. The temperature range of filled thermometers is very wide, approximately -200 to +700 °C. They are extremely robust but are not very high in accuracy. The application is mainly for process instrumentation and as stand-alone control devices. 

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... 

A test tube has a rounded bottom and is designed to hold and to heat small volumes of liquid. A Pasteur pipet is a small glass tube with a long thin capillary tip and a latex suction bulb. 

This group of methods can be subdivided into two subgroups (a) rise or depression inside thin capillaries or pores and (b) that outside objects. The former is the more pronounced feature rises can be substantial when the capillary is narrow and well-wetted. Moreover, it is of great practical relevance. A drawback is that precise profile measurements may be difficult because of optical distortion ). When the capillary is long and thin and the measuring liquid is a surfactant... 

Fig. 53. Schematic isotherms (density p versus chemical potential pi) corresponding to the gas-liquid condensation in capillaries of thickness D, for the case without (a) and with (b) prewetting, and adsorption isotherm (c) for a semi-infinite system, where the surface excess density pjs is plotted vs. pi. Full curves in (a) and (b) plot the density p vs. pi for a bulk system, phase coexistence occurs there between p,p, (bulk gas) and pn, (bulk liquid), while in the capillary due to the adsorption of fluid at the walls the transition is shifted from paKX to a smaller value rc(D, 7) (with pic(7>, T) 1 /D, the Kelvin equation ), and the density jump (from ps D) to pt D)) is reduced. Note also that in the ease where a semi-infinite system exhibits a first-order wetting transition 7W, for 7 > 7W one may cross a line of (first-order) prewetting transitions (fig. 54) where the density in the capillary jumps from p to p>+ or in the semi-infinite geometry, the surface excess density jumps from p to p +, cf. (c), which means that a transition occurs from a thin adsorbed liquid film to a thick adsorbed film. As pi the thickness of the adsorhed liquid film in the semi-infinite...

Fig. 54. Schematic phase diagrams for wetting and capillary condensation in the plane of variables temperature and chemical potential difference, (a) Refers to a case in which the semi-infinite system at gas-liquid condensation (ftaKX — d = 0) undergoes a second-order wetting transition at T = 7V The dash-dotted curves show the first-order (gas-liquid) capillary condensation at p = jt(I), T) which ends at a capillary critical point T v, for two choices of the thickness D. For all finite D the wetting transition then is rounded off. (b), (c) refer to a case where a first-order wetting transition exists, which means that ps remains finite as T - T and there jumps discontinuous towards infinity. Then for /iaKX - /i > 0 a transition may occur during which the thickness of the layer condensed at the wall(s) jumps from a small value to a larger value ( prewelting ). For thick capillaries, this transition also exists (c) but not for thin capillaries because then /Jcnn - (D,T) simply is loo large.

Let us consider the behavior of a liquid in a thin capillary tube immersed into a vessel containing the same liquid. Let us also assume that the radius of this capillary tube is sufficiently small so that the meniscus is spherical. If the wetting of capillary walls with the liquid is good (0<9O°), the curvature of fluid surface is negative (r<0), and the meniscus is concave (Fig. 1-13). The pressure under such meniscus is lower (as compared to what it would be under the flat surface) by the amount 2a/r, and thus, the fluid will rise inside the capillary, until it reaches the level at which the capillary pressure is balanced by the hydrostatic one, i.e... 

One of the methods of synthesis of clusters of uniform size consisting of just several atoms is the intrusion of liquid phase (e.g., mercury) under high pressure into zeolites with voids of different volume. High pressure is necessary for overcoming the capillary pressure in order to achieve filling of small voids with a liquid. When the pressure drops, the column of liquid in the thin capillary ruptures, similarly to the column of mercury in the thermometer upon cooling, and monodispersed clusters become trapped in the zeolite voids. Computer modeling and experimental studies of such small clusters both indicated that they form unique crystalline structures, impossible in the case of macroscopic crystals. For example, such structures may contain the axes of symmetry of fifth order. 

Summarizing, in the linear stability theory of capillary breakup of thin free liquid jets, the quasi-one-dimensional approach allows for a simple and straightforward derivation of the results almost exactly coinciding with those obtained in the framework of a rather tedious analysis of the three-dimensional equations of fluid mechanics. This serves as an important argument for further applications of the quasi-one-dimensional equations to more complex problems, which do not allow or almost do not allow exact solutions, in particular, to the nonlinear stages of the capillary breakup of straight thin liquid jets in air (considered below in this chapter). 

Goren, S. Gavis, J. Transverse wave motion on a thin capillary jet of a viscoelastic liquid. Phys. Fluids 4, 575-579 (1961). 

Mehring C, Sirignano WA, Nonlinear capillary wave distortion and disintegration of thin planar liquid sheets, J. Fluid Mech. 388, 69-113, 1999. 

Fig. 3.9 Raman spectroscopy of liquid samples in a thin capillary fiber (a) production of the fiber (b) incoupling of an argon laser beam with a microscope objective into the fiber and imaging of the outcoupled radiation into a spectrometer (c) fiber with liquid [320]...

The product contains moisture (usually water) mainly in the form of adsorbed liquid, capillary liquid, liquid causing the solid to swell or as bound liquid. Adsorbed liquid is a thin liquid film spread on the outer product surface. The vapor pressure above the liquid film corresponds to its saturation pressure at every temperature. Capillary liquid wets the inner pore surface of a porous solid. During the drying process, the liquid has to be transferred to the product surface by capillary forces. With products having macro capillaries of size >10 m, the vapor pressure still approximately cor-... 

Capillary columns may be coated with a thin, uniform liquid phase because of fused silica s smooth, inert surface, which generates a high efficiency, typically 3,000 to 5,000 theoretical plates per meter. Packed columns, on the other hand, have thicker, often nonuniform films, and generate only 2,000 plates per meter. Thus, total plates available in long capillary columns range from 180,000 to 300,000, while packed columns typically generate only 4,000 plates and show much lower resolution. 

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