The Flow of Liquids

The liquid state is a condensed state, so each molecule is always interacting with a group of neighbours although diffusing quite rapidly. As a result, although momentum through a shear plane still occurs, it is a small contribution when compared to the frictional resistance of the molecules in adjacent layers. It is the nature of this frictional resistance that we must now address and it will become clear that it arises from the intermolecular forces. The theories of the viscosity of liquids are still in an unfinished state but the physical ideas have been laid down. The first 

A consequence of the intermolecular forces is that any molecule in the liquid state has a large coordination number so that the structure has a low energy configuration. In other words there is short-range order in the liquid state. A significant amount of work must be done to remove a molecule from this structure - the latent heat of vaporisation. 

---

We defined the equation of motion as a general expression of Newton s second law applied to a volume element of fluid subject to forces arising from pressure, viscosity, and external mechanical sources. Although we shall not attempt to use this result in its most general sense, it is informative to consider the equation of motion as it applies to a specific problem the flow of liquid through a capillary. This consideration provides not only a better appreciation of the equation of... 

For the flow of liquids, expansion factor Y is unity. The change in potential energy in tne case of an inclined or vertical venturi meter must be allowed for. Equation (10-20) is accordingly modified to give... 

In the pulse bed shown in Figure 32, the liquid enters the bottom cone and leaves through the top cone. The flow of liquid is stopped periodically, spent carbon is withdrawn (pulsed) from the bottom, and virgin or reactivated carbon is added into the top of the adsorber. In a fixed-bed adsorber (illustrated in Figure 33), the liquid... 

We shall first consider the case of non-flashing liquids. In this situation, there is no critical flow pressure limiting the flow of liquid through a PR valve orifice, as opposed to the case of vapor flow. The discharge rate is a function of the pressure drop across the valve and can be estimated by the following expression ... 

Water hammer (also known as hydraulic shock) occurs in two distinct ways when the flow of liquid in a pipeline is suddenly stopped, for example, by quickly closing a valve [13], and when slugs of liquid in a gas line are set into motion by movement of gas or condensation of vapor. The latter occurs when condensate is allowed to accumulate in a steam main, because the traps are too few or out of order or in the wrong place. High-pressure mains have been ruptured, as in the following incident. 

At higher flow rates cavitation is a serious degradation mechanism, where vapor bubbles created by pressure fluctuations brought about by the flow of liquid past the surface collapse on the metal surface with tremendous force. This damages any protective oxide which may be present, leading to pitting corrosion. It also causes mechanical damage to the metal. 

Low condensing pressure operation should present no problem with float or electronic expansion valves, since these can open to pass the flow of liquid if correctly sized. 

To use such pipettes, a suitable pipette filler is first attached to the upper or suction tube. These devices are obtainable in various forms, a simple version consisting of a rubber or plastic bulb fitted with glass ball valves which can be operated between finger and thumb these control the entry and expulsion of air from the bulb and thus the flow of liquid into and out of the pipette. Suction by mouth must never be used to fill a pipette with liquid chemicals or with a solution containing chemicals. 

The osmotic pressure is a property that has proven to be especially valuable in the study of solutions of macromolecules, including those of biologic and polymeric interest. The apparatus for measuring this quantity is shown schematically in Figure 7.10. Two compartments are separated by a membrane that will allow the flow of liquid solvent between the two chambers. If solvent is added, flow will occur until the liquid level on the two sides of the membrane is the same. 

For the flow of liquid of depth s down a plane surface of width w inclined at an angle 0 to the horizontal, as shown in Figure 3.19, a force balance in the X-direction (parallel to the surface) may be written. In an element of length dr the gravitational force acting on that part of the liquid which is at a distance greater than y from the surface is given by ... 

The term F in equation 8.59 may be calculated directly for the flow of liquid through a uniform pipe. If a liquid is pumped through a height Az from one open tank to another... 

The flow of liquid in a 25 mm diameter pipe is metered with an orifice meter in which the orifice has a diameter of 19 mm. The aperture becomes partially blocked with dirt from the liquid. What fraction of the area can become blocked before the error in flowrate at a given pressure differential exceeds 15 per cent Assume that the coefficient of discharge of the meter remains constant when calculated on the basis of the actual free area of the orifice. 

Gruntfest U, Young JP, Jhonson NL (1964) Temperatures generated by the flow of liquids in pipes. J Appl Phys 35 18-23... 

Therefore, the velocities of liquid are consistent with the velocities of particles, that is, the motion of nano-particles can reflect the flow of liquid verily in the given condition. Figures 39 and 40 show the comparison of the two liquid samples with different mass concentration of the nanoparticles at different flow rates. Generally, particle velocity increases synchronously with the liquid flow rate, but the velocity becomes dispersive when it exceeds 300 /u,L/min. The more the particles were added in the liquid, the more dispersive of the velocities of the particles were observed. Several possible causes can result in this phenomenon. One possible reason is that when the velocity of flow becomes large enough, the bigger particles in the liquid cannot follow the flow as the smaller particles do, or bigger particles will move slower than the liquid around them, so the velocities of particles will distribute dispersedly. Another possible reason is that when the velocity of flow increases the time for particles to traverse, the view field of the microscope will decrease. As a result, the number of data points in the trace of a particle... 

Sparks due to static electricity associated with the separation of two dissimilar materials (Table 5.5). The charges may be transported/conducted some distance after separation before there is sufficient accumulation to produce a spark, e.g. in the flow of liquids or... 

S. G. Bankoff, Heat Conduction or Diffusion with Change of Phase George D. Fulford, The Flow of Liquids in Thin Films... 

Erosion Erosion of metal is the mechanical destruction of a metal by abrasion or attrition caused by the flow of liquid or gas (with or without suspended solids) in no manner is this metal loss an electrochemical corrosion mechanism (see Velocity Accelerated... 

The flow of liquid hydrocarbons can be enhanced by introducing into the stream a nonagglomerating suspension of ultra-high molecular weight polyethylene [490,1647] in water with small amounts of surfactant. The finely divided polyethylene is prepared by polymerization and then cryogrinded below the glass-transition temperature. 

The three reboilers in Figure 15.13 are shown under natural circulation. The flow of liquid from the column to the reboiler is created by the difference in hydrostatic head between the column of liquid feeding the reboiler and the vapor-liquid mixture created by the reboiler. 

The Flow of Liquids in Thin Films George D. Fulford... 

---