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| 2. |
- Andersson, Bengt-Åke, et al.
(författare)
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Bed-to-wall heat transfer in a 10m2 bubbling fluidized bed
- 1994
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Ingår i: Congreso Europeo de Fluidización. - 8478060936 ; 1, s. 251-260
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Konferensbidrag (refereegranskat)abstract
- The heat transfer is measured on the membrane tube wall in contact with a bubbling fluidized bed boiler. Measurements are carried out by heat transfer meters through holes in the wall both in the bed and above the bed in the splash zone and freeboard. Heat transfer coefficients are given and compared with previous measurements of material loss at the same wall and under the same conditions (typical for a fluidized bed boiler)
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| 3. |
- Andersson, Bengt-Åke, et al.
(författare)
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Experimental methods of estimating heat transfer in circulating fluidized bed boilers
- 1992
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Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 35:12, s. 3353-3362
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Tidskriftsartikel (refereegranskat)abstract
- Four different experimental methods have been used for the estimation of the bed-to-membranewall heat transfer in a 12 MW,, circulating fluidized bed boiler. The methods are compared for a case ofnormal operating conditions and the measured heat transfer coefficients are presented. In the central partof the combustion chamber where most of the cooling surface is located, the cross-sectional averagesuspension density normally varies in the range of 10-20 kg m -’ and the heat transfer coefficient is around130 W m ’ K-’ with a scatter of + 15% due to the different methods. The methods are critically analyzedand the heat transfer data are compared with relevant literature data.
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| 4. |
- Andersson, Bengt-Åke, et al.
(författare)
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Local lateral distribution of heat transfer on tube surface on membrane walls in CFB boilers
- 1993
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Ingår i: Proc of the 4th International Conference on Circulating Fluidized Beds. ; , s. 311-318
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Konferensbidrag (refereegranskat)abstract
- The wall to bed heat transfer was investigated in a 12 MWth CFB boiler at different locations in the combustion chamber and under various operating conditions. At high levels in the furnace the lateral distribution of heat flow to the tube and fin was found to be a result of radiation from the hot bed bulk, especially at low bulk densities. The local heat flow to the fin decreased considerably with decreasing height in contrast to the heat flow to the crest of the tube. This is due to the large down-flow of particles in the fin region and the growth of the boundary layer. The average heat transfer coefficient across the membrane wall was found to decrease with decreased bulk density, but at low bulk densities the decrease is very small since radiation dominates heat transfer.
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| 5. |
- Baskakov, A.P., et al.
(författare)
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Radiative transfer in circulating fluidized bed furnaces
- 1997
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Ingår i: Powder Technology. - 1873-328X .- 0032-5910. ; 90:3, s. 212-218
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Tidskriftsartikel (refereegranskat)abstract
- Three methods of estimating Ihe effective emissivily of a gas-particle suspension are eoml~ared and the radiative heat transfer coefficientof an isothermal suspension is defined. Heat flux measurements obtained from circulating fluidized bed comhustors are examined. Radiationfrom a particle suspension with core temperature dominates the radiative heat transfer in the upper part of the furnace, where the particledensity is low and no substantial particle boundary layers are formed. Over the lower pails of the heat transfer surfaces, where significantthermal and particle boundary layers are present, the radiative heat flux is dominated by emission from the relatively low temperature particlelayer in the vicinity of the heat receiving surface.
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| 6. |
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| 7. |
- Borodulya, A.V., et al.
(författare)
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Combustion kinetics of wood pellets in fluidized bed
- 1999
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Ingår i: News of National Academy of Sciences of Belarus (in Russian). Series of Engineering Physics Scs. No 2. ; , s. 115-123
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Breitholtz, Claes, 1967, et al.
(författare)
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Heat balance over the fluid-dynamic boundary layer of a circulating fluidized bed furnace
- 1998
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Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 41:8-9, s. 1013-1024
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Tidskriftsartikel (refereegranskat)abstract
- A heat balance over the fluid-dynamic boundary layer of a circulating fluidized bed furnace hasbeen formullated in order to calculate the heat transfer to the walls. The convective heat transfer is relatedto a horizontal particle flow from the core to the wall region, and an additive radiative heat transferconstituent is calculated for the particulate medium. An empirical description of the vertical distributionof solids and the transversal temperature profile are needed for the evaluation. The calculated heat transfercoefficients were compared with measurements in three commercial boilers and the deviation was less than40%, which is in the same order as the uncertainty of the experimental data.
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| 9. |
- Breitholtz, Claes, 1967, et al.
(författare)
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Heat transfer in circulating fluidized bed boilers - do we know sufficiently?
- 1997
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Ingår i: Trends in heat mass and momentum transfer. - 0973-2446. ; 3, s. 85-104
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Tidskriftsartikel (refereegranskat)abstract
- A considerable amount of work, mostly measurements, has been dedicated to heat transfer in circulating fluidized bed combustors. The results show that the radiative constituent of heat transfer varies between limits depending on the optical thickness of a particle boundary layer, and that the convective constituent can be related to the average cross-sectional suspension density. Based on this information reasonable estimates of heat transfer coefficients can be made. Experimental data from boiler conditions and ambient conditions are compared introducing a compensation for thermal radiation and changes in the properties of the gas with temperature. A good agreement is achieved between the two sets of data, except for cross-sectional average suspension densities below about 5 kg/m3. Locally there is a variation in heat transfer across the membrane-tube wall, and the heat transfer to the tube crest can be twice that to the adjacent fin. Heat transfer models are reviewed and applied to a hot (boiler) case and a cold (laboratory) case. The deviation of computed heat transfer coefficients from the measured ones was larger than the scatter in the measured data. The differences in the results from the models are primarily explained by uncertainties in the fluid-dynamic model parameters. For refined estimates and optimisation, knowledge of the detailed behaviour of the fluid-dynamics of the combustor is necessary. In this field the thickness of the a gas-gap between wall and particle suspension, the cover factor of the time-resolved fluctuating particle concentration, and the in-flow of particles towards the wall are insufficiently known and further work is necessary. In addition, further work is needed concerning the local heat transfer to membrane-tube walls
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| 10. |
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