Parallel streams

The sample solution flows onto a piece of fritted glass through which argon gas flows. The flow of argon is broken down into narrow parallel streams of high linear velocity, which meet the thin film of liquid percolating into the pores of the frit. At the interfaces, an aerosol is formed and is blown from the top of the frit. 

Figure 27.1 summarises the methodology for designing a component which must carry load. At the start there are two parallel streams materials selection and component design. A tentative material is chosen and data for it are assembled from data sheets like the ones given in this book or from data books (referred to at the end of this chapter). At the same time, a tentative component design is drawn up, able to fill the function (which must be carefully defined at the start) and an approximate stress analysis is carried out to assess the stresses, moments, and stress concentrations to which it will be subjected. 

In another version, a three-channel flow configruation is created for continuous water-oil-water or oil-water-oil parallel streams [29]. 

The liquid enters the micro channel device via a large bore that is connected to a micro channel plate via a slit (Figure 5.2). The slit acts as a flow restrictor and serves for equipartition of the many parallel streams [1, 3, 4]. The liquid streams are re-collected via another slit at the end of the micro structured plate and leave the device by a bore. The gas enters a large gas chamber, positioned above the micro channel section, via a bore and a diffuser and leaves via the same type of conduit. 

For most efficient utilization of the available reactor volume, all parallel streams that meet must have the same composition. 

The tests are run in two parallel streams the first stream is electrolyzed in... 

When the balance equations are formulated around individual units only, it is possible that the classification by output set assignment may not be satisfactory. Some variables classified as indeterminable may actually be determinable if we consider additional balances around groups of units. An erroneous measurement classification is also possible. The problem is in the system of equations used in the classification rather than in the assignment method. The most common problem arises because of the presence of parallel streams between two units. 

In order to analyze the existence of parallel streams, let us consider the case shown in Fig. 6 when total mass balances are included in the set of process constraints. The flowrate of stream 1 is assumed to be measured. By performing a material balance around each unit we have... 

To avoid these situations, we need to check for the presence of parallel streams in the flow diagram of the process. When this is the case, one of the individual balances is substituted by a combined balance around the units involved. 

However, analyzing the flow diagram we can see that units 3 and 4 are connected by parallel streams thus, the balance around unit 4 (b4) is substituted by a balance around unit 3 and 4 (b(3 + 4)). The new balances are now... 

Analysis of the process flowsheet to identify the presence of parallel streams. 

Varying the relative sizes of the flow regions as well as the flow rate of parallel streams allows great flexibility in matching the response curves of these models to that for the real vessel. Model F of this Figure has also been extended to j such units in series by Brothman et al. (B22). 

For the case of more or less parallel streams Danckwerts defined the degree of segregation by means of the age of a point. 

Such multi-platelet stacks were realized with tilted, straight (V-type) and curved (P-type) multi-channel arrays (see Figure 1.81) [41]. The V-type device has slanted outlets so that neighboring jets may collide the P-type has parallel streams. 

EOF has been applied as a pumping or mixing mechanism in microreactors (Fletcher et al., 2002). Mixing concepts include the introduction of two (or more, see Kohlheyer et al., 2005) parallel streams from a T- of Y-junction, where mixing at the low Reynolds numbers achieved occurs principally by interdiffusion of the two streams. This is a relatively slow process which may take tens of seconds to complete. Faster mixing can be achieved by injection of a sample of a specific composition via, for example, a double T-injector into a stream of liquid with a different composition. 

Mixing speed is controlled by the width of the injected plug, and will be much faster than in the parallel-stream case (Fletcher et al., 2002). 

A model by which this can be represented was proposed some years ago by Deans and Lapidus (3). A simple realization of this model is to consider the reactant as being divided into two parallel streams with different velocities, with the two streams being mixed and redivided at intervals. If this representation is to resemble a real packed reactor, the number of mixing-dividing points must be fairly large, say greater than 8 or 10. 

With the same notation as before, the reaction in one of the parallel streams can be described by... 

This arises when two layers of fluids (may not be of same species or density) are in relative motion. Thus, this is an interfacial instability and the resultant flow features due to imposed disturbance will be much more complicated due to relative motion. Physical relevance of this problem was seized upon by Helmholtz (1868) who observed that the interface as a surface of separation tears the flow asunder. Sometime later Kelvin (1871) posed this problem as one of instability and solved it. We follow this latter approach here. The basic equilibrium flow is assumed to be inviscid and incompressible - as two parallel streams having distinct density and velocity - flowing one over the another, as depicted in figure below. 

Transport from the gas phase to the micropore, which can take place by two parallel streams ... 

The time-varying turbulent motion of the bubble column seems to resemble the free turbulence of open jets (S4) or in the mixing zone of two parallel streams of different velocities (D13). 

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