Concentration profile modulator

Fig. 3. Analabs concentration profile modulator for exponential gradients, a = solvent 8 inlet, b = syringe barrel, c = plunger, d = piston seal, e = magnetic stirrer, f = to high-pressure pump.

Fig. 11. The mechanical valves can be replaced by thermal or chemical modulating devices. In principle, this modification circumvents the need of reliable mechanical valves and offers a more flexible system s . An example is the thermal oxidative modulation of methane in air. Figure 12 shows a concentration profile during 8 days, determined with an experimental modulation CC set up...

CMRs can offer viable solutions to the main drawback of homogeneous catalysis catalyst recycling. In addition, the membrane can actively take part in the reactive processes by controlling the concentration profiles thanks to the possibility to have membranes with well-defined properties by the modulation of the membrane material and structure. 

On the other hand, the treatment of M in a batch recirculation reactor system will generate a completely different concentration profile (Fig. 8-2, situation B). Small fractions of fluid are continuously removed from the batch tank and pumped through the photoreactor module (PR). Here, the same amount of OH... 

Concentration profiles of a solute in three-phase system transport through LM in a hollow-fiber module are similar to that, presented in Figure 13.3. 

FIGURE 37.7 Concentration profiles for Module 1 at the optimal point. 

At steady-state cadmium transport permeation is motivated mostly by an external driving force and the fluxes are about an order lower. A much more effective HLM module, with continuously flowing feed (open system), can be designed if the feed side membrane area Sp and the feed flow rate Up enable us to obtain a fixed cadmium feed outlet concentration (e.g., 1 ppm) at a contact time, less than that at the maximum on the simulated concentration profile of the carrier solution. 

FEMLAB. The FEMLAB software includes a partial differential equation solver. This edition includes a specially prepared version of FEMLAB on its own CD-ROM. With FEMLAB the students can view both axial and radial temperature and concentration profiles. Five of the FEMLAB modules are ... 

The simulation results provide detailed concentration profiles within the module. Figure 16.14 illustrates a typical radial concentration profile for a module cross-section along the tube sheet at the retentate outlet (i.e. the dry gas product end). Clearly radial variations in concentration exist. The shell concentration increases by 600% from the periphery of the fibre bundle to the centreline while the lumen concentration increases by 60%. The difference in lumen and shell concentrations decreases by 400%. 

Mathematical modeling and determination of the characteristic parameters to predict the performance of membrane solvent extraction processes has been studied widely in the literature. The analysis of mass transfer in hollow fiber modules has been carried out using two different approaches. The first approach to the modeling of solvent extraction in hollow fiber modules consists of considering the velocity and concentration profiles developed along the hollow fibers by means of the mass conservation equation and the associated boundary conditions for the solute in the inner fluid. The second approach consists of considering that the mass flux of a solute can be related to a mass transfer coefficient that gathers both mass transport properties and hydrodynamic conditions of the systan (fluid flow and hydrodynamic characteristics of the manbrane module). 

With the advent of sophisticated techniques such as molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MCXTVD), synthesis of heterostructure such as multiple quantum wells or superlattices with precise interface layer down to one monolayer have been routinely possible. This not only allows modulation of electronic properties such as carrier confinement and concentration profile, but also optical confinement and wave guiding properties with appropriate choice of refractive indices of the materials. Such precise controls over the growth and material properties have opened the field of band gap engineering . 

Figure 3 Effect of the Thiele modules on concentration profiles, = 2,(left) 4> -3 (right).

The concentration profiles are illustrated in Figure 5.22. The profiles are plotted with the Thiele modulus (cp) as parameters. The higher the value the Thiele module attains, the more profound the diffusion resistance inside the particle. 

FIGURE 5.22 Concentration profiles of a reactant in porous catalysts sphere (left) and slab (right), for different values of the Thiele module. 

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