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Abstract: This study is a sequel to the paper of Savage and Oger ( this issue) that reviewed experimental studies of airslides. These devices make use of fluidization to facilitate the transport of granular materials over long distances. The present paper describes a detailed and comprehensive consideration of the various contributions to the governing multiphase flow equations and proceeds to carry out numerical simulations of airslide flows and compare the results with laboratory experiments. It was carried out in part using the open source multiphase flow CFD program MFIX. Revisions and additions to the governing equations used in the distribution version of MFIX were made. The results of previously published molecular dynamics simulations were used to formulate a revised radial distribution function. The forms of the quasi-static stress contributions were designed to permit the development of higher concentration flows typical of experimentally observed airslide flows. Finally, additional terms were included in the particle fluctuation energy equation to account for (i) the viscous dissipation of the fluctuating particles due to the interstitial air, and (ii) the energy source term arising from the transfer of energy from the fluid to the particles. These expressions have been incorporated in the computational scheme and simulations of fluidized granular flows in a rectangular channel having frictional side walls were carried out. Some initial exploratory calculations were performed to examine the effects of various parameters on the mass flow rates and the velocity profiles. Different wall conditions were studied by varying the particle and wall restitution coefficients. The effects of varying the minimum fluidization velocity and the solid fraction thresholds were also examined. The simulation scheme was then applied to model two of the better documented fluidized chute flow experiments; those of Botterill and Bessant (1976), and the McGill University fluidized solids flow channel experiments of Liot (1979) and Chan (1979). Results of these computations and comparisons with observed experimental airslide behavior are discussed. Good agreement is found between the simulations and the experimental airslide flow characteristics. [Copyright &y& Elsevier]

Abstract: With the study object of an 100kt/a SL-II ethylene cracking furnace, this paper used Computational Fluid Dynamics (CFD) method to carry out coupled simulation studies on the flow, combustion, radiative heat transfer and thermal cracking reaction processes in the cracking furnace. The standard k–ε two-equation model was applied to turbulence simulation. The finite-rate/eddy-dissipation model was used for modeling of non-premixed combustion of the bottom burners and premixed combustion of the sidewall burners. The Discrete Ordinates (DO) model was applied to the simulation of radiative heat transfer of furnace. The simulation results show the detailed information about velocity, temperature and concentration fields in the furnace and heat flux distribution on the reactor tubes skin. This work will provide a theoretical basis for the optimization of the geometrical structure and operational parameters of the cracking furnace. [Copyright &y& Elsevier]