scholarly journals Modelling of the interaction of kinetics and external transport phenomena in structured catalysts: the effect of reaction kinetics, mass transfer and channel size distribution in solid foams

2021 ◽  
pp. 116815
Author(s):  
Tapio Salmi ◽  
Vincenzo Russo ◽  
Adriana Freites Aguilera
2019 ◽  
Vol 36 (1) ◽  
pp. 187-214
Author(s):  
Chao Yang ◽  
Guangsheng Luo ◽  
Xigang Yuan ◽  
Jie Chen ◽  
Yangcheng Lu ◽  
...  

Abstract This paper presents a comprehensive review of the remarkable achievements by Chinese scientists and engineers who have contributed to the multiscale process design, with emphasis on the transport mechanisms in stirred reactors, extractors, and rectification columns. After a brief review of the classical theory of transport phenomena, this paper summarizes the domestic developments regarding the relevant experiments and numerical techniques for the interphase mass transfer on the drop/bubble scale and the micromixing in the single-phase or multiphase stirred tanks in China. To improve the design and scale-up of liquid-liquid extraction columns, new measurement techniques with the combination of both particle image velocimetry and computational fluid dynamics have been developed and advanced modeling methods have been used to determine the axial mixing and mass transfer performance in extraction columns. Detailed investigations on the mass transfer process in distillation columns are also summarized. The numerical and experimental approaches modeling transport phenomena at the vicinity of the vapor-liquid interface, the point efficiency for trays/packings regarding the mixing behavior of fluids, and the computational mass transfer approach for the simulation of distillation columns are thoroughly analyzed. Recent industrial applications of mathematical models, numerical simulation, and experimental methods for the design and analysis of multiphase stirred reactors/crystallizers, extractors, and distillation columns are seen to garnish economic benefits. The current problems and future prospects are pinpointed at last.


2014 ◽  
Vol 749 ◽  
pp. 666-700 ◽  
Author(s):  
E. Russo ◽  
J. G. M. Kuerten ◽  
C. W. M. van der Geld ◽  
B. J. Geurts

AbstractWe propose a point-particle model for two-way coupling of water droplets dispersed in the turbulent flow of a carrier gas consisting of air and water vapour. We adopt an Euler–Lagrangian formulation based on conservation laws for the mass, momentum and energy of the continuous phase and on empirical correlations describing momentum, heat and mass transfer between the droplet phase and the carrier gas phase. An incompressible flow formulation is applied for direct numerical simulation of differentially heated turbulent channel flow. The two-way coupling is investigated in terms of its effects on mass and heat transfer characteristics and the resulting droplet size distribution. Compared to simulations without droplets or those with solid particles with the same size and specific heat as the water droplets, a significant increase in Nusselt number is found, arising from the additional phase changes. The Nusselt number increases with increasing ambient temperature and is almost independent of the heat flux applied to the walls of the channel. The time-averaged droplet size distribution displays a characteristic dependence on position expressing the combined effect of turbophoresis and phase changes in turbulent wall-bounded flow. In the statistically steady state that is reached after a long time, the resulting flow exhibits a mean motion of water vapour from the warm wall to the cold wall, where it condenses on average, followed by a net mean mass transfer of droplets from the cold wall to the warm wall.


Author(s):  
Le Xie ◽  
Qi-An Wang ◽  
Xian-Jin Luo ◽  
Zheng-Hong Luo

Abstract Solid particle dispersion and chemical reactions in high-viscosity non-Newtonian fluid are commonly encountered in polymerization systems. In this study, an interphase mass transfer model and a finite-rate/eddy-dissipation formulation were integrated into a computational fluid dynamics model to simulate the dispersion behavior of particles and the mass transfer–reaction kinetics in a condensation polymerization-stirred tank reactor. Turbulence fields were obtained using the standard k–ε model and employed to calculate the mixing rate. Cross model was used to characterize the rheological property of the non-Newton fluid. The proposed model was first validated by experimental data in terms of input power. Then, several key operating variables (i.e. agitation speed, viscosity, and particle size) were investigated to evaluate the dispersive mixing performance of the stirred vessel. Simulation showed that a high agitation speed and a low fluid viscosity favored particle dispersions. This study provided useful guidelines for industrial-scale high-viscosity polymerization reactors.


Fuel ◽  
2013 ◽  
Vol 108 ◽  
pp. 254-260 ◽  
Author(s):  
Yangxian Liu ◽  
Jianfeng Pan ◽  
Aikun Tang ◽  
Qian Wang

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