Influence of solids hydrodynamics on local heat transfer from tube banks immersed in a gas fluidized bed

Conference · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6682666

Moslemian, D; Chen, M M; Chao, B T

Fluidized bed combustion (FBC) has generated considerable interest as an efficient low-cost and non-polluting means of burning a variety of fuels. Despite the research and developmental efforts focused on FBC for more than three decades, the current state-of-the-art remains at a distance from the point where the combustor/boiler performance can be predicted with confidence. The high heat transfer rates and small internal temperature gradients as perceived from efficient mixing have yet to be fully realized. This is due largely to the multiplicity of variables involved in a fluidized bed combustor and the complexity of its hydrodynamics. Many empirical correlations for predicting heat transfer between a gas fluidized bed and the immersed internals have been proposed. They are based mainly on gross experimental observations with minimal attention to the mechanism of heat transfer due, at least in part, to the lack of systematic data on solids motion. Much useful insight can be obtained from a simultaneous determination of the local heat transfer rates from immersed internal structures and the associated hydrodynamics of the solid particles. Accordingly, in this study, the local mean heat transfer coefficients of horizontal internals simulating tube banks were measured for several locations in the bed along with measurements of the mean solids velocity and density distributions for a range of superficial gas velocities. The experiments were conducted in a 184 mm (7.25 in.) ID air fluidized bed with a horizontal in-line internal rod bundle of 16 mm (0.625 in.) OD with pitch-to-diameter ratio of 4 over a wide range of gas velocities. The results showed that the local heat transfer rates depend strongly on the flow pattern of solids induced by the bubble motion. The data confirmed the expectation that particle convection plays a major role in the mechanisms of heat transfer from immersed internals. 15 refs., 12 figs., 2 tabs.

• Research Organization: Illinois Univ., Urbana (USA). Dept. of Mechanical and Industrial Engineering
• DOE Contract Number: FG22-85PC80511
• OSTI ID: 6682666
• Report Number(s): CONF-861211-18; ON: DE87000863
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
014000* -- Coal
Lignite
& Peat-- Combustion
42 ENGINEERING
420400 -- Engineering-- Heat Transfer & Fluid Flow
BUBBLES
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
COAL
COMBUSTION
COMBUSTORS
CORRELATIONS
ENERGY SOURCES
ENERGY TRANSFER
FLUID MECHANICS
FLUIDIZED-BED COMBUSTION
FLUIDIZED-BED COMBUSTORS
FOSSIL FUELS
FUELS
HEAT TRANSFER
MATERIALS
MECHANICS
OXIDATION
PARTICLES
PARTICULATES
THERMOCHEMICAL PROCESSES
VELOCITY