Manifold flow channel

Ptdp) filtei. s. These filters employ one or more packs of filtermasse (cellulose fibers compressed to a compact cylinder) stacked into a pressure case. The packs are sometimes supported in individual trays which provide drainage channels and sometimes rest on one another with a loose spacer plate between each two packs and with a drainage screen buried in the center of each pack. The liquid being clarified flows under a pressure of 345 kPa (50 psig) or less through the pulp packs and into a drainage manifold. Flow rates are somewhat less than for disk filters, on the order of 20 L/(min-m ) [0.5 gal/ (min-ft")]. Pulp filters are used chiefly to polish beverages. The filtermasse may be washed in special washers and re-formed into new cakes. 

Some support structures are also included for detachably retaining the various components of the system. Preferably the support structure can be of the assembly board type , which provides prearranged flow channels and connector ports. The desired components of the system can be fastened into these connectors by pins. The flow control system that makes up the ICS system can include pumps, flow channels, manifolds, flow restrictors, valves, etc. These components are equipped with the necessary fittings that allow them to be sealed with the prearranged or selectively located flow channels or connectors. The flow system can also include detachable mixing devices, e.g., static or ultrasonic, or with a chip-like design. The reaction units, whether chip-like or not, can be of thermal, electrochemical, photochemical or pressure type [84]. 

As Fig. 12.1 indicates, the manifold cross section may be bead shaped and not circular. Thus, pressure flow in an elliptical cross-section channel may be more appropriate for the solution of the manifold flow. Such a problem, for Newtonian incompressible fluids, has been solved analytically. (J. G. Knudsen and D. L. Katz, Fluid Dynamics and Heat Transfer, McGraw-Hill, New York, 1958). See also, Table 12.4 and Fig. 12.51. 

Compatible plastics can flow through a single manifold reducing any potential problem down-stream in the multimanifold. Combinations can be made to provide different laminated designs. However, the final exiting layer thickness distributions can be affected by the amount of die body deflection if the die is not properly designed to take the required pressure loads. Any deflection causing distortion influences the melt flow channels (Chapter 17). 

Multiple, intersecting narrow channels can be formed on a glass chip to form a manifold of flow channels in which CE can be used to resolve a mixture of solutes in seconds. Harrison and co-workers... 

From the mathematical point of view the complexity is reduced because the system of equations which has to be solved is a function defined on the two-dimensional manifold of the control volumes boundary and leads to a dimension reduction. Practically the discretisation of the boundary usually is more simple than the meshing of complex three dimensional volumes. Especially this pertains to the transient flow channel geometry in co-rotating twin screw extruders. The surface meshes for the screws can independently be rotated inside the screw and barrel mesh analogous to the batchwise working internal mixer (Banbury Mixer) shown in the bottom part of Fig. 5.26. 

We have learned in previous sections that any flow-injection system is built around a flow channel of certain dimensions and geometrical form. It would therefore seem to be an easy matter to miniaturize it by simply scaling down existing manifolds. The difficulty is that such an approach will not yield microchannels, which would behave exactly like macro-... 

Figure 4.15. Three types of flow channel designs for stopped-flow injection analysis allowing options for selecting initial reaction time (/i) between injected sample ( /i) and reagent (B), mixing time (/m), delay time (fd), and stop time Us) of the sample within the flow cell (FC). While the system shown in (a) suffices for assays based on reaction rate measurements (cf. Figs. 4.12-4.14), physicochemical rate studies aimed at determining reaction rate constants require manifolds such as those depicted for slower bj and faster (c) reactions, the delay time required for sufficient radial mixing within the element of study (fm ") being a crucial parameter (d) C represents an inert carrier stream.

In Fig. 4.68 is shown a microconduit incorporating two potentiometric pH electrodes and a common reference electrode, the introduction of sample solution being executed by means of an exteriorly placed injection port. The measurement of pH requires a system with limited dispersion coefficient, and no chemical reaction is needed in the flow channel. Consequently, a short residence time was chosen, and the two pH-sensitive PVC-based membrane electrodes, containing as electroactive material tri- -dodecylamine [778], were placed in a single-line system and very close to the injection position (cf. Fig. 4.3), the Ag/AgCl wire reference electrode being situated in a side channel and connected to the main channel downstream from the indicator electrodes. The manifold construction is such that the reference solution and thus the liquid junction are renewed... 

To accomplish this, a) Place controllable and adequate heat sources at proper locations of the die heads and manifolds, b) Cover and insulate any large areas of exposed bare metal surfaces around die heads and manifolds. This is to prevent the heat loss through free convection, and to improve response time when heat is required. It also prevents the surface temperature of any localized area inside the flow channels to fall below the temperature of melt or worse yet, below melting point. In either case, melt next to these areas will slow down, stick, or freeze onto those surfaces. When changing color, they will be the sources of streaking. 

The cathode was a machined block of graphite with three parallel flow channels 2 mm x 2 mm x 30 mm long. The entire graphite block was press fit into a larger piece of Teflon for electrical isolation. The flow channels initiated and terminated in common manifolds in the Teflon block at either end of the graphite flow channels. The anode had the same chaimel structure, except that it was made of six graphite pieces separated by Teflon spacers inserted into a Teflon block, as shown in Figure 3.5A.An MEA was placed between the cathode and anode and sealed in the same way as for the differential fuel cell. 

Distribution of fluid from inlet manifolds into the fiber bundle (lumen and shell spaces) also can impact performance. This effect arises from pressure drops within the manifold that lead to different pressure drops across the flow channels within the bundle. 

Figure 13. Sources of non-ideal flows in hollow fiber bundles a) fluid distribution from the inlet manifold into the fiber bundle and b) fluid distribution within the fiber bundle. Fluid distribution from the lumen manifold into the fiber lumens (a, left hand side) can lead to higher flow rates in the fibers in the center of the bundle. Fluid distribution from the shell manifold (typically a fiber free collar that extends around the fiber bundle) into the shell can lead to higher flow rates near the inlet port than opposite it. Assuming a common pressure drop across all fibers lumen flows are higher in larger fibers (b, left hand side). Similarly, assuming a common pressure drop along flow channels in the shell, shell flows are higher in larger channels.

A common multilayer PP product is bi-axially oriented polypropylene (BOPP), produced on a line including a machine direction orientation unit, and a tenter frame for transverse orientation. This process commonly uses a three-manifold die that allows thin skin layers of copolymer to be applied on either side of a homopolymer base layer. The copolymer is used in this product so the film can be sealed, which is a requirement in packaging applications. Typically, the skin layer thickness is 5% of the total film thickness. The adhesive property of the copol3mier makes it difficult for the film to be processed through a tenter frame, because the film would stick to the tenter frame clips. The multimanifold die can be designed with narrower width flow channels for the skin layers, to keep the adhesive out of contact with the tenter clips, allowing the product to be extruded successfully. 

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