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连续搅拌反应器的元胞自动机模拟英文文献和中文翻译

时间:2017-12-04 21:24来源:毕业论文
AbstractThe classical dynamical systems model of continuous stirred tank reactors (CSTR) in which a first order chemical reaction takes place is reformulated in terms of the stochastic cellular automata procedure developed in the works of Se
Abstract−The classical dynamical systems model of continuous stirred tank reactors (CSTR) in which a first order chemical reaction takes place is reformulated in terms of the stochastic cellular automata procedure developed in the works of Seyborg [2] and Neuforth [3], which is extended by including the feed flow of chemical reactants. We show that this cellular automata model is able to simulate the dilution rate and the mixing process in the CSTR, as well as the details of the heat removal due to the jacket. The cellular automata approach is expected to be of considerable appli-cability at any industrial scale and especially for any type of microchemical system.16161
INTRODUCTION
A chemical reactor could be any vessel containing chemical reac-
tions. In general, a reactor is designed to maximize the yield of some
particular products while requiring the least amount of money to
purchase and operate. Normal operating expenses include energy in-
put, energy removal, raw material costs, labor, etc. Energy changes
can occur in the form of heating or cooling, or agitation. The latter
is quite important because an appropriate mixing has a large influ-
ence on the yield. Therefore, the design and operation of mixing
devices often determines the profitability of the whole plant.
In particular, in the widely developed continuous stirred tank reac-
tors (CSTR) one or more fluid reagents are introduced into a tank
equipped with an impeller while the reactor effluent is removed [1].
The impeller stirs the reagents to ensure proper mixing. Classical
CSTR dynamical models, based on coupled deterministic ordinary
differential equations (ODEs), are the usual approach to chemical
systems at the macroscopic scale. They have been demonstrated to
have considerable usefulness, but it should be mentioned that they
are based on the common assumption that spatial inhomogeneities
may be neglected. Thus, ODEs are a mean field approach and the 源自六-维+论\文"网*加7位QQ3249.114 www.lwfree.cn
analytical solutions of the ordinary differential equations (ODEs)
provide an accurate model only in this case.
When the system is not homogeneous, application of the above
assumption often yields a model that does not accurately represent
the system. This is the case, for example, of CSTRs with a highly
viscous medium where spatial heterogeneities exist in species con-
centrations, temperature, etc. Of course, the application of partial
differential equations (PDEs) to model spatial inhomogeneities such
as diffusion and hydrodynamic  turbulence may produce accurate
models. However, their solution requires advanced numerical tech-
niques such as finite element methods. Moreover, the numerical
techniques for solving the PDEs could be computationally expensive
and do not account for localized stochastic phenomena. In particu-lar, chemical systems are discrete from the microstructure until the
molecular level and statistical fluctuations in concentration and tem-
perature occur at these local scales.
Cellular automata are an attractive alternative to PDEs to model
complex systems with inhomogeneities of this type. A cellular auto-
mata lattice is comprised of discrete cells whose states are func-
tions of the previous state of the cell and its neighbors. Rules are
used to update each cell by scanning the value of the cells in the
neighborhood. Seyborg [2] and Neuforth [3] have shown that sto-
chastic cellular automata models can be successfully applied to simu-
late first order chemical reactions. In their papers, they worked on a
squared lattice of cells, each of them having a chemical reactant.
The reactions are performed by considering a probability of change,
from reactant A to product B, proportional to the kinetics constant
that defines the chemical equation. However, this type of calculation 连续搅拌反应器的元胞自动机模拟英文文献和中文翻译:http://www.lwfree.cn/fanyi/20171204/17371.html
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