Channel reaction simulation

Even for low-dimensional surfaces (three to six atoms), it is often difficult to design a well-behaved fitting function capable of yielding a balanced description of all reaction channels. A simulation of the reaction between an oxygen atom and methane, for example, requires a balanced energy description of the following (stable) species, as well as the reaction paths connecting these ... 

Also a simulation of the flow field in the methanol-reforming reactor of Figure 2.21 by means of the finite-volume method shows that recirculation zones are formed in the flow distribution chamber (see Figure 2.22). One of the goals of the work focused on the development of a micro reformer was to design the flow manifold in such a way that the volume flows in the different reaction channels are approximately the same [113]. In spite of the recirculation zones found, for the chosen design a flow variation of about 2% between different channels was predicted from the CFD simulations. In the application under study a washcoat cata-... 

The present book is devoted to both the experimentally tested micro reactors and micro reaction systems described in current scientific literature as well as the corresponding processes. It will become apparent that many micro reactors at first sight simply consist of a multitude of parallel channels. However, a closer look reveals that the details of fluid dynamics or heat and mass transfer often determine their performance. For this reason, besides the description of the equipment and processes referred to above, this book contains a separate chapter on modeling and simulation of transport phenomena in micro reactors. 

Monte Carlo simulations have been also used to reproduce the dynamics of adsorbates associated with NO reduction reactions. As mentioned above, complex desorption dynamics have been observed experimentally in some instances. For example, the N2 produced from decomposition of N20 on Rh(110) leaves the surface in five peaks associated with both the N20 dissociation events and the desorption of the adsorbed products. Monte Carlo simulations of those spectra was possible by using a model that takes into account both channels of N2 desorption and also N20 O lateral interactions to stabilize N20 adsorption [18],... 

Figure 19(a) shows the QM simulation of the differential cross-section (DCS) in the HF + D channel, over the same extended energy range as in Fig. 5. The agreement with experiment is seen to be qualitatively reasonable. The forward-backward peaking and direct reaction swathe observed in the experiment also occur in the QM calculation, although the relative magnitudes are not consistent. Thus fully quantitative agreement between QM calculations and experiment in all of the reaction attributes must await further refinements of the PES, and/or a more rigorous treatment of the open-shell character of the F(2P) atom.90...

Fig. 3. The normalized excitation functions in A2 versus collision energy for the two isotopic channels for the F+HD reaction. The solid line is the result of quantum scattering theory using the SW-PES. The QCT simulations from Ref. 71 are plotted for comparison. The experiment, shown with points, is normalized to theory by a single scaling factor for both channels. Also shown in (a) is the theoretical decomposition of the excitation function into direct and resonant contributions using the J-shifting procedure.

Studies of ferredoxin [152] and a photosynthetic reaction center [151] have analyzed further the protein s dielectric response to electron transfer, and the protein s role in reducing the reorganization free energy so as to accelerate electron transfer [152], Different force fields were compared, including a polarizable and a non-polarizable force field [151]. One very recent study considered the effect of point mutations on the redox potential of the protein azurin [56]. Structural relaxation along the simulated reaction pathway was analyzed in detail. Similar to the Cyt c study above, several slow relaxation channels were found, which limited the ability to obtain very precise free energy estimates. Only semiquantitative values were... 

The inclusion of chemical reaction into CFD packed-tube simulations is a relatively new development. Thus far, it has been reported only by groups using LBM approaches however, there is no reason not to expect similar advances from groups using finite volume or finite element CFD methods. The study by Zeiser et al. (2001) also included a simplified geometry for reaction. They simulated the reaction A + B - C on the outer surface of a single square particle on the axis of a 2D channel (Fig. 16). 

This paper describes a simulator which has been developed at the Alberta Research Council and permits gasification in a two-ton coal block. Initial gasification experiments with air, steam and carbon dioxide are summarized, and data for product gas composition, heat propagation through the coal block, and gasification rates as functions of the geometry of the reaction channel are presented. 

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