A general numerical model is presented here to describe the complex fluid dynamics and the heat transfer process in high-temperature circulating fluidized beds (CFBs). The core-wall concept is used to describe the gas-solid flow in the dilute phase section of CFBs. The variation of the thickness of the wall layer along the height direction is considered in the fluid dynamic model in order to approach the practical conditions. Three components of heat transfer, i.e., the particle-convective heat transfer, the gas-convective heat transfer, and the radiative heat transfer, and their contributions to the total heat transfer coefficient are investigated. The influences of some operating parameters on the total heat transfer and its components are predicted. Detailed information about the mechanism of heat transfer is discussed. The radiative heat transfer accounts for about 3060% of the total heat transfer in high temperature CFBs. It gradually increases along the height direction of the furnace. When the contribution of particle convection increases, the contribution of gas convection decreases, and vice versa. Particle size shows a significant effect on the radiative heat transfer and the convective heat transfer. High bed and wall temperatures will primarily increase the radiative heat transfer.

1.
Grace, J. R., 1986, “Heat Transfer in Circulating Fluidized Bed,” Circulating Fluidized Bed Technology, ed., P. Basu, Pergamon Press, pp. 63–82.
2.
Basu
,
P.
,
Nag
,
P. K.
,
Chen
,
B. H.
, and
Shao
,
M.
,
1987
, “
Effect of Operating Variables on Bed to Wall Heat Transfer in a Circulating Fluidized Bed
,”
Chem. Eng. Commun.
,
61
, pp.
227
237
.
3.
Martin
,
H.
,
1984
, “
Heat Transfer between Gas Fluidized Beds of Solid Particles and the Surfaces of Immersed Heat Exchanger Elements
,”
Chem. Eng. Process.
,
18
, pp.
157
169
.
4.
Glicksman, L. R., 1988, “Circulating Fluidized Bed Heat Transfer,” Circulating Fluidized Bed Technology II, eds., P. Basu and J. F. Large, Pergamon Press, pp. 13–29.
5.
Chen
,
C. C.
, and
Chen
,
C. L.
,
1992
, “
Experimental Study on the Bed-to-Wall Heat Transfer in a Circulating Fluidized Bed
,”
Chem. Eng. Sci.
,
47
, No.
5
, pp.
1017
1025
.
6.
Basu, P., and Konuche, F., 1988, “Radiative Heat Transfer from a Fast Fluidized Bed,” Circulating Fluidized Bed Technology II, eds., P. Basu and J. F. Large, Pergamon Press, Oxford, pp. 245–254.
7.
Basu
,
P.
,
1990
, “
Heat Transfer in Fast Fluidized Bed Combustors
,”
Chem. Eng. Sci.
,
45
, No.
10
, pp.
3123
3136
.
8.
Chen, J. C., Cimini, R. J., and Dou, S. S., 1988, “A Theoretical Model for Simultaneous Convective and Radiative Heat Transfer in Circulating Fluidized Bed,” Circulating Fluidized Technology II, eds., P. Basu and J. F. Large, Pergamon Press, Oxford, pp. 255–262.
9.
Leckner, B., 1991, “Heat Transfer in Circulating Fluidized Bed Boilers,” Circulating Fluidized Bed Technology III, eds., P. Basu and M. Horio, Pergamon Press, Oxford, pp. 27–38.
10.
Kunii
,
D.
, and
Levenspiel
,
O.
,
1997
, “
Circulating Fluidized-Bed Reactors
,”
Chem. Eng. Sci.
,
52
, No.
15
, pp.
2471
2482
.
11.
Werther, J., 1994, “Fluidized Mechanics of Large-Scale CFB Units,” Circulating Fluidized Bed Technology IV, ed., A. Avidan AIChE, New York, NY, pp. 1–14.
12.
Qi, C., and Farag, I. H., 1993, “Heat Transfer Mechanism due to Particle Convention in Circulating Fluidized Bed,” preprint volume, 4th International Conference on CFB, USA, pp. 396–401.
13.
Zehner
,
P.
, and
Schlunder
,
E. U.
,
1970
, “
Warmeleitfahigkeit von Schuttungen bei massigen Temperaturen
,”
Chem.-Ing.-Tech.
,
42
, pp.
933
941
.
14.
Hunt
,
M. L.
, and
Tien
,
C. L.
,
1988
, “
Non-Darcian Convection in Cylindrical Packed Beds
,”
ASME J. Heat Transfer
,
110
, pp.
378
384
.
15.
Chandrasekhar, S., 1960 Radiative Transfer. Dover. New York, NY.
16.
Flamant, G., 1985, “Transfert de chaleur couple´s dans les lits fluidise´s a` haut tempe´rature. Application a` la conversion thermique de l’e`nergie solaire,” the`se de docteur Es-Science, No. 93, Institut National Polytechnique de Toulouse, Mar 4.
You do not currently have access to this content.