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Title: Predictive models of circulating fluidized bed combustors

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:
OSTI Identifier:
7195746
Report Number(s):
DOE/PC/89769-T12
ON: DE93000938
DOE Contract Number:
FG22-89PC89769
Resource Type:
Technical Report
Research Org:
Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical Engineering
Sponsoring Org:
DOE; USDOE, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; COAL; FLUIDIZED-BED COMBUSTION; FLUIDIZED-BED COMBUSTORS; MATHEMATICAL MODELS; CIRCULATING SYSTEMS; EXPERIMENTAL DATA; PROGRESS REPORT; CARBONACEOUS MATERIALS; CHEMICAL REACTIONS; COMBUSTION; COMBUSTORS; DATA; DOCUMENT TYPES; ENERGY SOURCES; FOSSIL FUELS; FUELS; INFORMATION; MATERIALS; NUMERICAL DATA; OXIDATION; THERMOCHEMICAL PROCESSES 014000* -- Coal, Lignite, & Peat-- Combustion