Fluid mixes, semi

Wang, Y. D., and R. Mann (1990). Mixing in a stirred semi-batch reactor partial segregation for a pair of competing reactions analyzed via networks-of-zones, Inst. Chem. Eng. Symp. Ser., 121(Fluid Mixing 4), 241-258. 

Semi-permeable membranes are quasi-two-dimensional barriers which, given a fluid mixture of two or more species of particles (usually two different molecular species, mixed or in solution) on one side, allow the passage either way through the membrane of one or more, but not all, of the molecular species, in either direction. This gives the possibility of separating, at... 

The IAD I(a,t) in a chemical reactor is specially interesting and it does not seem that sufficient attention has been paid to the possibilities offered by this function. For instance, let us consider a semi-batch reactor, and let Q(t) be the feed flowrate of an incompressible fluid. The instantaneous fluid volume is V = /q Q(tf)dtf, from which the IAD is written I(a,t) = Q(t-a)/V. I(a,t) can be used to calculate the chemical conversion in different segregation states. Consider a species of concentration C produced with the rate t. If the mixture is assumed to be well mixed at the molecular scale, one obtains the familiar mass balance equation... 

Various methods of contacting fluids with particulate solids are shown in Figure 5.13. These contacting methods include countercurrent, crosscurrent, and cocurrent plug flow as well as mixed solids flow-intermediate gas flow, and semi-batch operations. Consideration of the residence time distribution for each type of fluid-solid contact is necessary to understand its effect on the conversion. As a result of given residence time distribution, E t), the average conversion of B, Xb, is given by... 

FIGVRES.13 Various contacting patterns in fluid-solid reactors (a-c) countercurrent, crosscurrent, and cocurrent plug flow (d) intermediate gas flow, mixed solid flow (e) semi-batch operations. From Levenspiel [1], copyright 1972 by John Wil r Sons, Inc. Reprinted by permission of John Wiley Sons, Inc. 

The system we consider here is a semi-infinite porous medium having a uniform porosity f, and a uniform permeability k, a finite thickness L (the smaller lateral dimension) in the direction, and a finite width hL in the direction. The gravity acts in the z[ direction. The magnitude of the fluid velocity has a uniform value vj over the injection face. We will consider two cases in which the injection fluid is well mixed and diffusion upstream of the injection face can be neglected. Either the composition at the injection face is or it increases linearly with time from... 

Simulations confirm that these are regions where fluid trajectories are well- mixed. This provides a basis for constructing FAM s for dispersion in these regions using semi-analytical diffusivity models. 

There are various types of restricted-access packings that have been developed for sample clean-up. Reviews by Unger (1991) and Haginaka (1991) discuss internal-surface reversed phases, shielded hydrophobic phases, semi-permeable surfaces, dual-zone phases, and mixed functional phases. The majority of these packings have been developed to purify drugs from body fluids. 

Problem 10-10. Mixing Layer. Two semi-infinite streams of the same fluid, but with different uniform, parallel velocities, Uand all, are brought into contact. Owing to the action of viscosity, a boundary layer will develop over which the initial discontinuity in velocity will be smoothed out as illustrated in the figure. Derive the boundary-layer equations for... 

Figure 3. Effect of compaction on mix densities for stiff and semi-fluid...

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