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Jinghai Li - One of the best experts on this subject based on the ideXlab platform.

  • a multiscale Mass Transfer Model for gas solid riser flows part 1 sub grid Model and simple tests
    Chemical Engineering Science, 2008
    Co-Authors: Weigang Dong, Wei Wang, Jinghai Li
    Abstract:

    The gas-solid Mass Transfer in circulating fluidized bed (CFB) riser flow is both structure-dependent and dynamic in nature. Recent progress in multiscale computational fluid dynamics (CFD) allows fresh insight into the dynamic flow structure, yet its influence on the Mass Transfer remains to be settled. To this end, a multiscale Mass Transfer Model is established in this paper based on the extended framework of the energy-minimization multiscale (EMMS) Model. The relevant algorithm named EMMS/Mass is proposed for CFD-coupled Mass Transfer computation. Two testing cases accounting for sublimation of naphthalene and decomposition of ozone, respectively, are presented to demonstrate the characters of the Model. It is shown that structural consideration can have significant effects on the Model prediction. The normally used Reynolds number is not adequate to characterize these effects, while the combination of gas velocity and solids flux seems to capture the structural effects and allows to explain the variation of Sherwood number reported for CFB risers in the literature. Sub-grid coupling of this multiscale Mass Transfer Model and CFD approach can be expected to provide a promising tool to probe the dynamic and structure-dependent nature of Mass Transfer in CFB risers. (C) 2008 Elsevier Ltd. All rights reserved.

  • a multiscale Mass Transfer Model for gas solid riser flows part ii sub grid simulation of ozone decomposition
    Chemical Engineering Science, 2008
    Co-Authors: Weigang Dong, Wei Wang, Jinghai Li
    Abstract:

    This article is to test the EMMS-based multiscale Mass Transfer Model through computational fluid dynamics (CFD) simulation of ozone decomposition in a circulating fluidized bed (CFB) reactor. Three Modeling approaches, namely types A, B and C, are classified according to their drag coefficient closure and Mass Transfer equations. Simulation results show that the routine approach (type C) with assumption of homogeneous flow and concentration overestimates the ozone conversion rate, introduction of structure-dependent drag force will improve the Model prediction (type B), while the best fit to experimental data is obtained by the multiscale Mass Transfer approach (type A), which takes into account the sub-grid heterogeneity of both flow and concentration. In general, multiscale behavior of Mass Transfer is more distinct especially for the dense riser flow. The fair agreement between our new Model with literature data suggests a fresh paradigm for the CFB related reaction simulation.

Weigang Dong - One of the best experts on this subject based on the ideXlab platform.

  • a multiscale Mass Transfer Model for gas solid riser flows part 1 sub grid Model and simple tests
    Chemical Engineering Science, 2008
    Co-Authors: Weigang Dong, Wei Wang, Jinghai Li
    Abstract:

    The gas-solid Mass Transfer in circulating fluidized bed (CFB) riser flow is both structure-dependent and dynamic in nature. Recent progress in multiscale computational fluid dynamics (CFD) allows fresh insight into the dynamic flow structure, yet its influence on the Mass Transfer remains to be settled. To this end, a multiscale Mass Transfer Model is established in this paper based on the extended framework of the energy-minimization multiscale (EMMS) Model. The relevant algorithm named EMMS/Mass is proposed for CFD-coupled Mass Transfer computation. Two testing cases accounting for sublimation of naphthalene and decomposition of ozone, respectively, are presented to demonstrate the characters of the Model. It is shown that structural consideration can have significant effects on the Model prediction. The normally used Reynolds number is not adequate to characterize these effects, while the combination of gas velocity and solids flux seems to capture the structural effects and allows to explain the variation of Sherwood number reported for CFB risers in the literature. Sub-grid coupling of this multiscale Mass Transfer Model and CFD approach can be expected to provide a promising tool to probe the dynamic and structure-dependent nature of Mass Transfer in CFB risers. (C) 2008 Elsevier Ltd. All rights reserved.

  • a multiscale Mass Transfer Model for gas solid riser flows part ii sub grid simulation of ozone decomposition
    Chemical Engineering Science, 2008
    Co-Authors: Weigang Dong, Wei Wang, Jinghai Li
    Abstract:

    This article is to test the EMMS-based multiscale Mass Transfer Model through computational fluid dynamics (CFD) simulation of ozone decomposition in a circulating fluidized bed (CFB) reactor. Three Modeling approaches, namely types A, B and C, are classified according to their drag coefficient closure and Mass Transfer equations. Simulation results show that the routine approach (type C) with assumption of homogeneous flow and concentration overestimates the ozone conversion rate, introduction of structure-dependent drag force will improve the Model prediction (type B), while the best fit to experimental data is obtained by the multiscale Mass Transfer approach (type A), which takes into account the sub-grid heterogeneity of both flow and concentration. In general, multiscale behavior of Mass Transfer is more distinct especially for the dense riser flow. The fair agreement between our new Model with literature data suggests a fresh paradigm for the CFB related reaction simulation.

Wei Wang - One of the best experts on this subject based on the ideXlab platform.

  • a multiscale Mass Transfer Model for gas solid riser flows part 1 sub grid Model and simple tests
    Chemical Engineering Science, 2008
    Co-Authors: Weigang Dong, Wei Wang, Jinghai Li
    Abstract:

    The gas-solid Mass Transfer in circulating fluidized bed (CFB) riser flow is both structure-dependent and dynamic in nature. Recent progress in multiscale computational fluid dynamics (CFD) allows fresh insight into the dynamic flow structure, yet its influence on the Mass Transfer remains to be settled. To this end, a multiscale Mass Transfer Model is established in this paper based on the extended framework of the energy-minimization multiscale (EMMS) Model. The relevant algorithm named EMMS/Mass is proposed for CFD-coupled Mass Transfer computation. Two testing cases accounting for sublimation of naphthalene and decomposition of ozone, respectively, are presented to demonstrate the characters of the Model. It is shown that structural consideration can have significant effects on the Model prediction. The normally used Reynolds number is not adequate to characterize these effects, while the combination of gas velocity and solids flux seems to capture the structural effects and allows to explain the variation of Sherwood number reported for CFB risers in the literature. Sub-grid coupling of this multiscale Mass Transfer Model and CFD approach can be expected to provide a promising tool to probe the dynamic and structure-dependent nature of Mass Transfer in CFB risers. (C) 2008 Elsevier Ltd. All rights reserved.

  • a multiscale Mass Transfer Model for gas solid riser flows part ii sub grid simulation of ozone decomposition
    Chemical Engineering Science, 2008
    Co-Authors: Weigang Dong, Wei Wang, Jinghai Li
    Abstract:

    This article is to test the EMMS-based multiscale Mass Transfer Model through computational fluid dynamics (CFD) simulation of ozone decomposition in a circulating fluidized bed (CFB) reactor. Three Modeling approaches, namely types A, B and C, are classified according to their drag coefficient closure and Mass Transfer equations. Simulation results show that the routine approach (type C) with assumption of homogeneous flow and concentration overestimates the ozone conversion rate, introduction of structure-dependent drag force will improve the Model prediction (type B), while the best fit to experimental data is obtained by the multiscale Mass Transfer approach (type A), which takes into account the sub-grid heterogeneity of both flow and concentration. In general, multiscale behavior of Mass Transfer is more distinct especially for the dense riser flow. The fair agreement between our new Model with literature data suggests a fresh paradigm for the CFB related reaction simulation.

James R Fair - One of the best experts on this subject based on the ideXlab platform.

  • distillation columns containing structured packings a comprehensive Model for their performance 2 Mass Transfer Model
    Industrial & Engineering Chemistry Research, 1996
    Co-Authors: J A Rocha, Jose L Bravo, James R Fair
    Abstract:

    This is the second part of a two-part paper dealing with the fluid mechanics and Mass Transfer in structured packings for distillation column service. The first part elucidated pressure drop, flooding, and liquid holdup. The second part covers the generation of effective interfacial area and provides a general correlation for predicting the Mass-Transfer efficiency as a function of surface type, packing geometry, phase flow conditions, and fluid properties. The Mass-Transfer Model has been tested against a variety of commercial structured packings, for distillation pressures ranging from 0.33 to 20.4 bar. In all cases the fit of the data is excellent, with the possible exception of the highest pressures, where additional factors of axial mixing appear to have an effect.

John C Little - One of the best experts on this subject based on the ideXlab platform.

  • an analytical Mass Transfer Model for predicting voc emissions from multi layered building materials with convective surfaces on both sides
    International Journal of Heat and Mass Transfer, 2007
    Co-Authors: H P Hu, Yang Zhang, Xinke Wang, John C Little
    Abstract:

    Abstract An analytical Mass Transfer Model for predicting emissions of Volatile Organic Compounds (VOCs) from multi-layered building materials and the instantaneous VOC material-phase distribution is developed. Different from the Mass Transfer Models in the literature, it is able to describe the characteristics of VOC emissions from a wall with an arbitrary number of layers of different materials and with convective surfaces on both sides, and it does not neglect the Mass Transfer resistance through the gas-phase boundary layer. The Model is validated with experimental data from the literature. The Model provides a powerful tool for predicting VOC emissions from composite materials such as furniture and layered wall structures. Based upon the Model and the dimensionless analysis, the applicable condition of Kumar and Little’s double-layer Model is discussed.