Processing multi-scale

As a practice-based subject, the formation and development of tribology have always been associated with the requirement from society and technology development. Tribology experienced several different stages in its history. Its developing process indicates an obvious trend of integration and combination of multi-scientific subjects in a multi-scale nature from macroscopic dimension to nanometre. 

Bakshi, B. R., and Stephanopoulos, G., Representation of process trends. Part III. Multi-scale extraction of trends from process data. Comput. Chem. Eng. 18, 267 (1994a). 

Hessel and Lowe report on hybrid, i.e. multi-scale, approaches which are currently most often favored for micro-reactor plant construction, simply for practical time and cost reasons [9, 10]. In addition, such an approach allows one to fit micro reactors in existing industrial, producing and academia, measuring environments. The micro reactor is only used where it is really needed and costs for changing the processing are kept to a minimum in such a way (Figure 1.9). 

The realization of complete bench-scale micro reactor set-ups is certainly still in its infancy. Nevertheless, the first investigations and proposals point at different generic concepts. First, this stems from the choice of the constructing elements for such set-ups. Either microfluidic components can be exclusively employed (the so-caUed monolithic concept) or mixed with conventional components (the so-called hybrid or multi-scale concept). Secondly, differences concerning the task of a micro-reactor plant exist. The design can be tailor-made for a specific reaction or process (specialty plant) or be designated for various processing tasks (multi-purpose plant). 

Apart from these ACSYS projects, a number of new research programs have been developed, such as the Study of Environmental Arctic Change (SEARCH), which is an interdisciplinary, multi-scale program dedicated to understanding the complex of interrelated changes that have been observed in the Arctic environment in the past few decades (Morison, 2001 Morison and Calder, 2001). SEARCH is envisioned as a long-term effort of observations, modeling, process studies, and applications with emphasis on five major thematic areas ... 

From the multi-scale point of view, the total energy dissipation Nj can be grouped into three portions, namely, Nsurf, Nturb, and Nbreak- The last portion is generated from bubble breakage and finally dissipated in the process of bubble coalescence. While Nsurf and Nln rb are considered to be directly dissipated on micro-scale, Nbreak is counted as a kind of meso-scale energy dissipation. Therefore, the stability condition can be either expressed with the minimization of micro-scale energy dissipation Nsurf + Nturb 7 min or conveyed as the maximization of meso-scale energy dissipation Nbreak max. 

Zhao, H., Multi-scale Modeling of Gas-Liquid (Slurry) Reactors, Ph.D. thesis (in Chinese), Institute of Process Engineering, Chinese Academy of Sciences, Beijing (2006). 

This section deals with multi-scale models for the PEFC and consists of three subsections, 4.1,4.2, and 4.3, that relate to molecular-level models, bridging models between scales and device/process level models, respectively. The objectives of these subsections are to survey the development and application of these models. 

The demand for the research will cover the development of the novel algorithms utilizing parallel computation methods. The development of a hierarchical multi-scale paradigm will consolidate theoretical analysis and will lead to large-scale decision-making criteria of the process level design based on the first-principle dynamics. 

An old classic but now particularly relevant process, carbon dioxide (C02) capture with alkanolamines, is used in the most industrially oriented of the contributions to illustrate that integrated, high fidelity, multi-scale... 

Figure 1.2 Design and development cycle for mixing-field based design there is a selection of the mixing equipment based on the process requirements. This leads to the specification of a mixing field. CFD simulations give the flow field reduced to a multi-scale mixing model.

Development of multi-scale models for powder compaction processing... 

Gradually we have come to recognize that understanding of the spatio-temporal multi-scale structures in various chemical processes is essential for upgrading our ability. In fact, as much as we know about macro-scale chemical processing, e.g., radial and axial profiles, and what happens at micro-scales, e.g., chemical reaction and even molecular structures, we really know little about what happens at the meso-scale in between. That is, meso-scale is the key to understanding multi-scale structures. This is the bottleneck ... 

Different scales presented in Figure 3-1 are related to different approximation levels. For an overview of conventional molecular modelling methods, (see e.g.1-3). Bridging the above mentioned disparate time scales for the description of biologically relevant collective motions requires hierarchical, multi-scale approaches. In practice, to describe real complex (bio)molecular or material systems and processes various models have to be coupled to each other. Selected coupling mechanisms will be briefly reviewed. 

Kohout, M., Collier, A.P., and Stepanek, F. Vacuum Contact Drying Multi-Scale Modeling and Experiments, in European Symposium on Computer Aided Process Engineering - 14 (A. Barbosa-Povoa, and H. Matos Eds.), pp. 1075-1080. Elsevier Science, Amsterdam (2004). 

In all of the above cases, a strong non-linear coupling exists between reaction and transport at micro- and mesoscales, and the reactor performance at the macroscale. As a result, the physics at small scales influences the reactor and hence the process performance significantly. As stated in the introduction, such small-scale effects could be quantified by numerically solving the full CDR equation from the macro down to the microscale. However, the solution of the CDR equation from the reactor (macro) scale down to the local diffusional (micro) scale using CFD is prohibitive in terms of numerical effort, and impractical for the purpose of reactor control and optimization. Our focus here is how to obtain accurate low-dimensional models of these multi-scale systems in terms of average (and measurable) variables. 

In effect, such a multi-scale analysis resolves a macro-scale heterogeneous system into three meso- to micro-scale subsystems—dense-phase, dilute-phase and inter-phase. Thus, modeling a heterogeneous particle-fluid two-phase system is reduced to calculations for the three lower-scale subsystems, making possible the application of the much simpler theory of particulate fluidization to aggregative fluidization and the formulation of energy consumptions with respect to phases (dense, dilute and inter) and processes (transport, suspension and dissipation). 

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