Surface to fluidized bed heat transfer

Botterill, J.S.M.; Desai, Meha

doi:10.1016/0009-2509(70)85107-7

Cited by 12 publications

(19 citation statements)

References 4 publications

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“…Then, it follows from equation (7-4) that We shall observe that for range of parameters considered, the roots of the quadratic equation (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) always have negative real parts. We also observe that the constraint _:quation (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) is always satisfied for the range of parameters.…”

Section: I_1mentioning

confidence: 96%

“…Using equations (3-2), (3-4)-(3-6), (3)(4)(5)(6)(7), and (4-1)-(4.-5) we can rewrite (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) in the non-dimensional form. as…”

Section: Conservation Of Linear Momentum For the Fluid Constituentmentioning

confidence: 99%

“…c51 and _2 are zero. Then, the set of equations (6-8) - (6)(7)(8)(9)(10)(11)(12)(13)(14)(15) reduces to the following set of eight simple homogeneous algebraic equations:…”

Section: I_1mentioning

confidence: 99%

“…where the C's in equations (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) are given by, (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) where, A caref_al investigation in these equations (6-21)- (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) Anderson and Jackson, we use a procedure similar to theirs to obtain a quadratic equation in the growth number. We set parameters 0_1°,0_2°and 0_4°to be zero.…”

Section: I_1mentioning

confidence: 99%

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Stability of flows in fluidized beds

Rajagopal¹

1992

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DE92 017669 DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United Stat_,s Government.Neither the Unit¢_t States Government nor any agency th,;r¢of, nor any of their cmp[oy_s, makes any warrant)', express or implied, or assum¢:s any legal liability or r_sponsi-bility for the accuracy, completeness, or usef'ulne.ss of' any information, apparatus, product, or process disclo_d, or rcpr¢_nts that ks use would not infringe privately own_ rights. Reference: herein to any specific _mmercial product, proc,css, or service by trade name, trademark, rna)_ufacturer, or otherwise does not r_e,_saril), constitute or imply its endorsement, r¢com-mc)_dation, or favoring by th.¢ United States Government or any agency thereof. The q¢ws an, d opinions of authors exprcss_ herein do not r_c_,_.ssarily state or rcfl_t tho_ of the United States Oov©rnmcnt or any agency thc,rc_f.

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Section: I_1mentioning

confidence: 96%

“…Using equations (3-2), (3-4)-(3-6), (3)(4)(5)(6)(7), and (4-1)-(4.-5) we can rewrite (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) in the non-dimensional form. as…”

Section: Conservation Of Linear Momentum For the Fluid Constituentmentioning

confidence: 99%

“…c51 and _2 are zero. Then, the set of equations (6-8) - (6)(7)(8)(9)(10)(11)(12)(13)(14)(15) reduces to the following set of eight simple homogeneous algebraic equations:…”

Section: I_1mentioning

confidence: 99%

Section: I_1mentioning

confidence: 99%

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Stability of flows in fluidized beds

Rajagopal¹

1992

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“…Temperature-time data is plotted as It is noteworthy to mention that, due to the mixing and turbulence in the fluidized beds, the heat transfer coefficient between the floating sample and the bed was of the order of (100-400) W/m 2 K [Botterill, (1975)]. Using the Chilton-Colburn analogy, the convection moisture transfer coefficient ( 2 kg m s ) was calculated from the heat transfer coefficient by the following equation:…”

Section: Calculation Of the Overall Heat Transfer Coefficientmentioning

confidence: 99%

Theoretical and experimental drying of a cylindrical sample by applying hot air and infrared radiation in an inert medium fluidized bed

Honarvar

Mowla

2012

Braz. J. Chem. Eng.

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-Drying of a cylindrical sample in a fluidized bed dryer containing inert particles was studied. For this purpose, a pilot-scaled fluidized bed dryer was constructed in which two different heat sources, hot air and infrared radiation were applied, and pieces of carrot were chosen as test samples. The heat transfer coefficient for cylindrical objects in a fluidized bed was also measured. The heat absorption coefficient for carrot was studied. The absorption coefficient can be computed by dividing the absorbed heat by the carrot to the heat absorbed for the water and black ink. In this regard, absorbed heat values by the carrot, water and black ink were used A mathematical model was proposed based on the mass and heat transfer phenomena within the drying sample. The results obtained by the proposed model were in favorable agreement with the experimental data.

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Heat transfer characteristics in a small-scale fluidized bed boiler

Tia

Suwanayuen

Tangsatitkulchai

et al. 1996

Int. J. Energy Res.

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SUMMARYHeat transfer characteristics in a small-scale fluidized bed boiler (2 MW, ) were studied using lignite and corn cob as fuels. Depending on air velocity, the heat transfer rates from bed to water membrane wall and from hot flue gas to convective tube bank were in the ranges 7 5 5 5 % and 25-45% of the total heat absorbed by the boiler, respectively. At designed capacity, the heat transfer flux based on bed cross sectional area and on water membrane wall area were about 045 and 015MWm-2, respectively. Under the conditions studied, it was found that the overall heat transfer coefficient between bed and water membrane wall was 100-300Wm-2K-1, whereas that between flue gas and convective tube bank was 10-30Wm-* K-l. The study of heat transfer to a horizontal tube immersed in the bed as well as placed in the freeboard region were also studied. The effective heat transfer coefficients were found to be 300-800Wm-2K-' for in-bed tube and 30-150Wm-2 K-' for the freeboard region, depending on air velocity. Comparison of these data with those predicted by both modelling and correlation reported in the literature was also made. For the immersed tube, good agreement was observed for low air velocity, while at high air velocity the experiment produced results twice those estimated from modelling and correlation. For the freeboard region, the model gave a fair prediction.KEY WORDS: fluidized bed heat transfer combustion boiler 1. INTRODUCTION One of the features of fluidized beds that make this technology attractive for use in industrial coal/biomass fired boilers is the high heat transfer capability between bed and surface. Enhancement of heat transfer characteristics not only significantly reduces the heat transfer area but also allows the transfer process to occur at low bed temperature (1000-1200K), thereby decreasing NO, emission. The effective heat transfer coefficient for tubes immersed in the bed is an order of magnitude higher than that for tubes placed on the free board region or in the fixed bed. The difference can be utilized to control the boiler output by lowering and raising the bed level to vary the portions of the exchanger tubes exposed in the freeboard or by stopping the air supply to the individual cells of the bed.Studies of the heat transfer characteristics of fluidized beds, both experimental and theoretical models, have recently been reviewed in the literature (Botterill, 1986;Xavier and Davidson, 1985;Mathur and Saxena, 1987; Kunii and Levenspiel, 1991). It was found that the heat transfer between the surface immersed in the bed and that placed in the freeboard region is affected by solid and gas properties, fluidization conditions, types of air distributor, bed dimensions, temperature and pressure. The develop ment of a heat transfer model from first principles has achieved limited success owing to the chaotic behaviour of the system. For high temperature operation such as in the combustor, the contribution of radiation to the total heat transfer cannot be ignored, which increases the degree of ...

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Surface to fluidized bed heat transfer

Cited by 12 publications

References 4 publications

Stability of flows in fluidized beds

Stability of flows in fluidized beds

Theoretical and experimental drying of a cylindrical sample by applying hot air and infrared radiation in an inert medium fluidized bed

Heat transfer characteristics in a small-scale fluidized bed boiler

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