Modeling and simulating the drying of grass seeds (Brachiaria brizantha) in fluidized beds: evaluation of heat transfer coefficients

Jr.A.C., Rizzi; Passos, M. L.

doi:10.1590/s0104-66322009000300010

Cited by 6 publications

(12 citation statements)

References 2 publications

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“…However, as pointed out by Yates, [4] there is a deviation from this theory since W actually decreases as the particle diameter increases. As shown in the previous work [12] for coarse particles belonging to Geldart group D, W equals to 0.26 under the bubbling regime and to 1 under the continuously slugging regime. Equation (6) and correlations presented in Table 2 for particles from group D have already been incorporated into the model for better describing the gas flow in fluidized Type of slug:…”

Section: Bubble Gas Phasesupporting

confidence: 59%

“…[12,13] Incorporating such correlations into the model, the first attempt to simulate heat transfer between bubble-gas-particles in beds of grass seeds (Brachiaria brizantha) has been made. [12] Based on these results, the present work aims at modifying this three-phase model for simulating the drying of these seeds in batch fluidized beds, taking into account: (a) transience of heat and mass transfer mechanism; (b) shrinkage of particles as water evaporates; and (c) drying kinetics including both the constant rate and the falling rate.…”

Section: Modeling the Drying Of Grass Seeds (Brachiaria Brizantha) Inmentioning

confidence: 99%

“…Modifications Model Fluid Flow Based on previous works, [12,13] one can see in Table 2 that gas flows quite differently in fluidized beds of group D particles than it flows in fluidized beds of group B particles.…”

Section: Bubble Gas Phasementioning

confidence: 99%

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Modeling the Drying of Grass Seeds (Brachiaria brizantha) in Fluidized Beds

et al. 2007

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A modified three-phase model is developed to simulate the drying of Brachiaria brizantha in fluidized beds. In this new model, the constitutive equation of drying kinetics is formulated including both the constant rate and the falling rate mechanisms; the seed shrinkage is taken into account during all drying operation and the transition between bubbling to slugging regime is delineated for estimating the bubble velocity and size. Such modifications improve the mathematical model to better simulate the drying of coarse particles in fluidized beds. The best estimation of the five adjustable model parameters, which are required to define heat and mass transfer mechanisms between interstitial gas and seed particles and to specify the heat loss from dryer walls to ambient air, is attained by incorporating an optimization routine into the computer model program. Having been specially designed to supply data for this model, experiments are performed in a bath laboratory-scale fluidized bed. Additional data are generated to validate the model and program routines. Results show a good agreement between simulated and experimental data, validating the approach used to describe drying kinetics and particle shrinkage.

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Section: Bubble Gas Phasesupporting

confidence: 59%

Section: Modeling the Drying Of Grass Seeds (Brachiaria Brizantha) Inmentioning

confidence: 99%

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Modeling the Drying of Grass Seeds (Brachiaria brizantha) in Fluidized Beds

et al. 2007

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“…Some authors [6,7] use the theory of bubbling bed model for the completion of numerical simulations, where the heat transfer characteristics are well examinable. There are heat and mass transfer between the phases, as:…”

Section: Bubbling Bed Modelmentioning

confidence: 99%

Determination of entry length of a fluidized bed dryer using volumetric heat transfer coefficient

Poós

Szabó

2017

IRASE

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Fluidized bed dryers are widely used in several fi elds of industry. Suffi ciently accurate thermal models provide an opportunity to increase the effectiveness of dryers. The required size of a fl uidized bed dryer can be defi ned with the application of mathematical model. This work is aimed at developing mathematical model to investigate the infl uence of operating parameters in a fl uidized bed dryer using volumetric heat transfer coeffi cient. After the defi ning the input parameters of the differential equations, the required entry length of the dryer which effective heat and mass transfer between gas and particles takes place can be estimated. The correct estimation of the entry length is useful in optimal design of a fl uidized bed dryer. Using the model the impact of the drying parameters can be determined to the required length. Keywords: fl uidized bed dryer, heat and mass transfer, volumetric heat transfer coeffi cient, mathematical model

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“…The lumped method was used to measure the value of the average heat transfer coefficient h t (Salagnc et al, 2004;Rizzi et al, 2009). For this purpose a piece of metal with high thermal conductivity was placed in the fluidized bed to find the h t value.…”

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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Modeling and simulating the drying of grass seeds (Brachiaria brizantha) in fluidized beds: evaluation of heat transfer coefficients

Cited by 6 publications

References 2 publications

Modeling the Drying of Grass Seeds (Brachiaria brizantha) in Fluidized Beds

Modeling the Drying of Grass Seeds (Brachiaria brizantha) in Fluidized Beds

Determination of entry length of a fluidized bed dryer using volumetric heat transfer coefficient

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

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