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 in the chapter on kinetic theory. Here the conventional derivation resented in single phase fluid mechanics is generalized to multiphase flow.
- Research Organization:
- Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical Engineering
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-89PC89769
- OSTI ID:
- 7195746
- Report Number(s):
- DOE/PC/89769-T12; ON: DE93000938
- Country of Publication:
- United States
- Language:
- English
Similar Records
Predictive models of circulating fluidized bed combustors. 14th Technical progress report
Predictive models of circulating fluidized bed combustors: SO[sub 2] sorption in the CFB loop
Related Subjects
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