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Title: Predictive models of circulating fluidized bed combustors. 12th technical progress report

Abstract

Steady flows influenced by walls cannot be described by inviscid models. Flows in circulating fluidized beds have significant wall effects. Particles in the form of clusters or layers can be seen to run down the walls. Hence modeling of circulating fluidized beds (CFB) without a viscosity is not possible. However, in interpreting Equations (8-1) and (8-2) it must be kept in mind that CFB or most other two phase flows are never in a true steady state. Then the viscosity in Equations (8-1) and (8-2) may not be the true fluid viscosity to be discussed next, but an Eddy type viscosity caused by two phase flow oscillations usually referred to as turbulence. In view of the transient nature of two-phase flow, the drag and the boundary layer thickness may not be proportional to the square root of the intrinsic viscosity but depend upon it to a much smaller extent. As another example, liquid-solid flow and settling of colloidal particles in a lamella electrosettler the settling process is only moderately affected by viscosity. Inviscid flow with settling is a good first approximation to this electric field driven process. The physical meaning of the particulate phase viscosity is described in detail inmore » the chapter on kinetic theory. Here the conventional derivation resented in single phase fluid mechanics is generalized to multiphase flow.« less

Authors:
Publication Date:
Research Org.:
Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical Engineering
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10184041
Report Number(s):
DOE/PC/89769-T12
ON: DE93000938
DOE Contract Number:  
FG22-89PC89769
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jul 1992
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; COAL; FLUIDIZED-BED COMBUSTION; FLUIDIZED-BED COMBUSTORS; MATHEMATICAL MODELS; PROGRESS REPORT; EXPERIMENTAL DATA; CIRCULATING SYSTEMS; 014000; COMBUSTION

Citation Formats

Gidaspow, D. Predictive models of circulating fluidized bed combustors. 12th technical progress report. United States: N. p., 1992. Web. doi:10.2172/10184041.
Gidaspow, D. Predictive models of circulating fluidized bed combustors. 12th technical progress report. United States. https://doi.org/10.2172/10184041
Gidaspow, D. 1992. "Predictive models of circulating fluidized bed combustors. 12th technical progress report". United States. https://doi.org/10.2172/10184041. https://www.osti.gov/servlets/purl/10184041.
@article{osti_10184041,
title = {Predictive models of circulating fluidized bed combustors. 12th technical progress report},
author = {Gidaspow, D},
abstractNote = {Steady flows influenced by walls cannot be described by inviscid models. Flows in circulating fluidized beds have significant wall effects. Particles in the form of clusters or layers can be seen to run down the walls. Hence modeling of circulating fluidized beds (CFB) without a viscosity is not possible. However, in interpreting Equations (8-1) and (8-2) it must be kept in mind that CFB or most other two phase flows are never in a true steady state. Then the viscosity in Equations (8-1) and (8-2) may not be the true fluid viscosity to be discussed next, but an Eddy type viscosity caused by two phase flow oscillations usually referred to as turbulence. In view of the transient nature of two-phase flow, the drag and the boundary layer thickness may not be proportional to the square root of the intrinsic viscosity but depend upon it to a much smaller extent. As another example, liquid-solid flow and settling of colloidal particles in a lamella electrosettler the settling process is only moderately affected by viscosity. Inviscid flow with settling is a good first approximation to this electric field driven process. The physical meaning of the particulate phase viscosity is described in detail in the chapter on kinetic theory. Here the conventional derivation resented in single phase fluid mechanics is generalized to multiphase flow.},
doi = {10.2172/10184041},
url = {https://www.osti.gov/biblio/10184041}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jul 01 00:00:00 EDT 1992},
month = {Wed Jul 01 00:00:00 EDT 1992}
}