Continuous tortuous paths

Figure 4. Continuous tortuous paths, water/decane. Water is the dark phase, oil is the clear phase. Ca = 1.5 x 10". ...

Sprayed coatings have structures in which fine pores thread tortuous paths through the deposit, and it is necessary to apply a coating thickness of about 350 ftm if all these paths are to be closed. Scratch-brushing of the deposit, however, makes it possible to consolidate the surface and to achieve adequate continuity in thinner deposits, e.g. 200 m. 

Because they do not obey the octet rule, hypervalent molecules have often been thought to involve some type of bonding that is not found in period 2 molecules. Ideas concerning the nature of this bonding have developed along a somewhat tortuous path that it is interesting and instructive to follow. We will in the end conclude that the nature of the bonding in these molecules is not different in type from that in related period 2 molecules and that there is therefore little justification for the continued use of this concept. 

Dispersive forces due to the tortuous path of the fluid, matrix deformation, and diffusion are neglected. Taking the same steps as for the continuity equation, we get... 

The allowable current density—normality ratio for electric membrane operation has been approximately doubled by an improved tortuous path spacer with strap turbulence promoters and by operation at higher pressures up to 60 p.s.i. As a result, twice as much water can now be demineralized per square foot of membrane utilized and/or greater demineralization achieved per pass in electric membrane units. One practical result of this development is a new continuous-flow, two-stage single-stack demineralizer which will provide 93% demineralization at a capacity of 5000 gallons per day and 72% demineralization at a capacity of 30,000 gallons per day. These units produce from 67 to 150% more water per unit membrane area than previously used automatic batch-recirculating units and are far simpler in construction and operation. 

Impingement and Coalescence. Impingement separation relies upon the difference in momentum, either between a gas particle and a liquid droplet, or between two liquid droplets. It occurs when liquid-laden gas approaches a coalescing device or target (e.g., wire mesh pad, vane element, or filter cartridge). This coalescing device causes the gas to follow a tortuous path, while the liquid droplets continue in a straighter path as. a result of... 

The transport properties of polymer blends are of interest both for the practical application of blends and for providing insight into the morphology of the blend. Measurement of the effect of blend composition on permeability in various rubbers has been described [49i].The permeability of elastomer blends depends on the concentration of the continuous phase and the morphology of the dispersed phase. Extended disperse phase structures, particularly lying in a stacked or lamellar configuration, can lead to a reduced permeability because of the more tortuous path that must be taken by penetrants [49]]. 

Blown-film coextrusion presents the added difficulty of obtaining a continuous barrier layer. A die with a crosshead mandrel is preferred over a die with a spiral mandrel, because the spiral mandrel tends to lead to long residence time in the spirals. A standard crosshead mandrel, however, results in a weld line where the barrier layer is not continuous. As shown in Figure 15, this problem is solved by providing an overlap of the barrier layer at the weld line (206). Although the barrier layer is not continuous across the weld line, sufficient overlap will create a tortuous path for permeation, and the barrier properties will be maintained... 

Barrier Phenomenon. In red cell filtration, the blood first comes into contact with a screen filter. This screen filter, generally a 7—10-) m filter, does not allow micro aggregate debris through. As the blood product passes through the deeper layer of the filter, the barrier phenomenon continues as the fiber density increases. As the path becomes more and more tortuous the cells are more likely to be trapped in the filter. 

These diagrams demonstrate that the SMNs should be well dispersed in the continuous phase, monodis-perse, and small in size. This can be visualized if one assumes that the SMNs in the diagrams are 5 nm particles. Thus, there would be four layers of particles between the dispersed phase regions. If one replaces the 5 nm particles with 20 nm particles, then a single 20 nm particle will essentially take up the same space (linearly) as four 5nm particles. Replacing the 5nm particles with 20 nm particles makes the path to coalesce or flocculation less tortuous. Also, at equal weights of particles, there are fewer 20 nm particles than 5 nm particles. It is well known that the viscosity... 

Under normal vessel loading conditions, the rate of bitumen coalescence is slow relative to the rate at which bitumen droplets collect at the interface. As a consequence, much of the occluded water cannot drain. Paths for drainage become exceedingly tortuous as the froth interface is continually replenished with aerated bitumen droplets. 

The gas relative permeability, Pr, is defined as the permeability of a fluid through a porous medium partially blocked by a second fluid, normalized by the permeability through the same porous solid, when the pore space is free of this second fluid. In most cases, the gas relative permeability diminishes at the percolation threshold , at which a significant portion of the pores are still conducting but they don t form a continuous path through the membrane along the direction of flow. The tortuous capillary model fails to predict this the percolation threshold arises only when all pores are blocked by capillary condensation. In comparison, the network model can provide a satisfactory analysis of the percolation threshold problem, without, as noted earlier, increasing the number of the model parameters. 

Whenever three to nine theoretical stages are necessary, packed columns are the preferred devices. The packing provides a tortuous flow path for the dispersed phase, thereby increasing contact time between phases. The packing also restricts axial mixing of the continuous phase. Sieve-plate columns also have been employed for these same applications. The perforations in the trays serve to produce the dispersion, while the downcomers (or upcomers) conduct the continuous phase from tray to tray. Sieve plates create a series of short spray columns with the continuous phase being partially mixed in the downcomers. Because packed and sieve-trayed columns impart only a minimum of energy to the system, they are preferred for low interfacial tension systems (less than 12 dyne/cm) to avoid emulsification. 

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