Flow orientation

Molecules of nematic Hquid crystals also are aligned in flow fields which results in a viscosity that is lower than that of the isotropic Hquid the rod-shaped molecules easily stream past one another when oriented. Flow may be impeded if an electric or magnetic field is appHed to counter the flow orientation the viscosity then becomes an anisotropic property. 

Calvert (R-12) has tested the correlation in cross-flow packed beds, which tend to give better drainage than countercurrent beds, and has found the effect of gas-flow orientation insignificant. However, the onset of reentrainment was somewhat lower in a bed of 2.5-cm... 

Further improvements in the properties of PAN-based carbon fibers are likely to emerge through improved stabilization, that is, by creating the ideally cross-linked fiber. On the other hand, as purer pitch precursors become available, further improvements in mesophase pitch-based carbon fibers are likely to arise from optimized spinnerette designs and enhanced understanding of the relationship between pitch chemistry and its flow/orientation behavior. Of course, the development of new precursors offers the potential to form carbon fibers with a balance of properties ideal for a given application. 

Vortex formation is a condition that arises from centrifugal acceleration acting on gravitational acceleration. The circular motion of the entire contents of the tank predominates over the flow of the liquid from the impeller. Flow orientation thus is important not only in cases of noticeable vortex formation, but... 

There are substantial influences on a material created by the flow orientation of the molecules, so there are different properties in the flow direction and perpendicular to the flow. These differences have a significant effect on the performance of the part (Chapter 2). 

However, many reactions of commercial interest have chemistry, mechanical, or system requirements that preclude the use of cross-flow reactors. Processes cannot use a cross-flow orientation primarily because of high temperatures and the need to internally recuperate heat such as steam methane reforming (SMR) [12, 13] and oxidation reactions [14]. Counter- and coflow devices require a micromanifold to dehver sufficiently uniform flow to each of the many parallel channels. 

Figure 2.10 Multilamination flow oriented along the computational grid (left) and forming a tilted angle with the grid cells (right).

The interdigital feed can be fed in a counter-flow or co-flow orientation the first principle is realized in metal/stainless steel or silicon/stainless steel devices [39, 41], the latter in glass chip devices [40, 44 6]. 

For fibers or tubular modules, the feed is generally introduced into the inside of the tubes, or lumen, while permeate is withdrawn from the shell side. This flow orientation enhances the shear at the membrane surface for TFF operation. These modules may also be run at high conversion or NFF mode with the feed introduced on the outside of the tubes or shell side. In this case, the shell side offers greater surface area. 

We now report that in the region of the absorption band the flow linear dichroism of a solution of 1 is positive (Fig. 3). Assuming that the nature of the flow orientation is of the usual kind, i.e., that the polymer chains in a random coil conformation which dominates in solution (34) tend to align with the flow direction, this observation provides additional support for the absolute assignment of the transition moment direction along the chain direction, even in solution. Similar conclusions based on polarization studies on a stretched film of poly(di-n-hexyl silane) have recently been reported (36). 

Ueda et al. [26] recently investigated a flow-oriented PE-fr-aPP diblock copolymer with Mw = 113 000 (Mn/Mw = 1.1) and a PE volume fraction of 0.48. This diblock copolymer is in the strong segregation regime (i.e., estimated xN = 10.5 and Todt = 290 °C) and has a lamellar morphology in the melt. They found a breakout phenomenon with the formation of spherulites in an intermediate crystallization temperature range 95 < Tc < 101 °C. At crystallization temperatures above 101 °C or below 95 °C spherulites were not formed and the crystallization was confined within the lamellar MD. Ueda et al. report that lamellar MD and spherulites do not co-exist when the material crystallizes from the melt which is separated in lamellar MDs. In other words, in this particular case, breakout or confined crystallization within lamellar MDs depends on the crystallization conditions. 

Although as-spun fibers of Cl-HQ/BB/TA with m/n = 70/30 exhibited a modulus of 95 GPa, as-spun fibers of Cl-HQ/BB/TA with m/n = 80/20 exhibited a lower modulus of only 11 GPa in spite of the more rigid chemical structure due to the decreased elongational flow orientation, as shown in Figure 19.3.1 Tensile-fractured as-spun fibers of Cl-HQ/BB/TA with m/n = 70/30 exhibited many fibrils when compared to those of Cl-HQ/BB/TA with m/n = 80/20. 

The lower modulus seemed to be referred to the lower elongational flow orientation. Tensile-fractured as-spun fiber of Me-HQ/BB/NDA with m/n = 92.5/7.5 exhibited many fibrils when compared to Me-HQ/BB/NDA as-spun fiber with m/n = 95/5, as shown in Figure 19.5. 

The moduli of as-spun fibers of polyarylates depend highly upon the stability of the liquid crystalline state, the rigidity of the polymer chain, and the degree of elongational flow orientation (F-value). On the other hand, the moduli of injection molded specimens of polyarylates depend upon the stability of the liquid crystalline state, and the rigidity and packing density of the polymer chain. 

Once the design parameters are identified, sizing of the SCR catalyst follows. Typically, a multilayer SCR reactor is considered with the flue gas directed in a vertical down flow orientation. Some U.S. refiners have installed bypasses around the... 

There has been much interest in flow and flow orientation effects with polymer melts containing anisometric particles which may be plate-like or fibrous. Flow-induced orientation of short reinforcing fibres is an area of considerable commercial importance, which is beyond the scope of the review [30]. 

Hanratty TJ, Eckelmann LD, Fortuna G (1972) Drag reduction and the wave length of flow-oriented wall eddies Nature Phys Sci 236 94... 

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