A First Principles–Neural Networks Approach to Model a Vibrated Fluidized Bed Dryer: Simulations and Experimental Results

Álvarez, Pedro; Blasco, R.; Gómez, J.; Cubillos, Francisco

doi:10.1081/drt-200047661

Cited by 18 publications

(7 citation statements)

References 11 publications

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“…(14) and (17) and have to be calculated as limit values. The integral terms in the solutions contain the inlet conditions and are obtained numerically from the inlet liquid content or temperature gradients.…”

Section: Modeling Ofmentioning

confidence: 99%

“…[12] Recently, a model based on the concept of a drying coefficient to describe the resistance against internal moisture transport was developed for a batch vibrating fluidized bed dryer. [13] This type of dryer has also been modeled by a neural network approach [14] that takes into account the back-mixing effect by establishing interconnected drying zones. The model included the mass and energy balances for each zone in the solid phase, and complete mixing was assumed in the gas phase.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mathematical Modeling of a Continuous Vibrating Fluidized Bed Dryer for Grain

Picado

Martínez

2012

Drying Technology

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Section: Modeling Ofmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mathematical Modeling of a Continuous Vibrating Fluidized Bed Dryer for Grain

Picado

Martínez

2012

Drying Technology

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“…This gives a much lower product residence time per unit bed area than non-vibrating beds [62]. Vibration increases particle diffusivity, constant drying rate [62][63][64] and falling drying rate [65][66][67]. Drying rate also increases with increasing amplitude and gas superficial velocity [59,64].…”

Section: Vibrated Fluidized Bedmentioning

confidence: 99%

“…Vibration increases particle diffusivity, constant drying rate [62][63][64] and falling drying rate [65][66][67]. Drying rate also increases with increasing amplitude and gas superficial velocity [59,64]. However, the understanding of transport processes in the vibrated fluidized bed dryer is still little known even 20 years after the first effort was started [68].…”

Section: Vibrated Fluidized Bedmentioning

confidence: 99%

Fluidized Bed Dryers — Recent Advances

Daud¹

2008

adv powder technol

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Although industrial fluidized bed dryers have been used successfully for the drying of wet solid particles for many years, the development of industrial fluidized bed dryers for any particular application is fraught with difficulties such as scaling-up, poor fluidization and non-uniform product quality. Scaling-up is the major problem and there are very few good, reliable theoretical models that can replace the expensive laboratory work and pilot-plant trials. This problem is mainly due to the different behavior of bubbles and mixing regimes in fluidized bed dryers of different size. Simple transformation of laboratory batch drying data to continuous back-mixed dryers using the residence time distribution of the solids is insufficient to account for the complex flow and heat and mass transfer phenomena occurring in the bed. Although time scaling using temperature driving forces and solids mass flux for the same change in moisture content in the batch and continuous dryers has been successful in predicting moisture content profiles in the continuous dryer at the constant rate period, it does not take into account solid mixing. Two-phase Davidson-Harrison models have been used in modeling of the continuous back-mixed dryer with various degrees of success. On the other hand, the three-phase Kunii-Levenspiel model is seldom used in modeling fluidized bed dryers because it is too complex to handle. A combination of multi-phase models and residence time distribution could improve predicting power for back-mixed dryers because this combination takes into account both the bubbles and solid mixing phenomena. Incremental models were widely used to model continuous plug flow fluidized bed dryers, but the cross-flow of drying medium has not been sufficiently modeled except by the author. In some incremental models, axial dispersion is modeled using the Peclet number, Pe. A combination of an incremental model with an axial dispersion and cross-flow model of drying medium would improve predicting power. Poor fluidization of Geldart group C particles could be improved by the assistance of external means such as vibration, agitation, rotation and centrifugation. Both vibrated and agitated fluidized bed dryers have been successfully used in industry, but rotating or centrifugal fluidized bed dryers are still not available for industrial use. Nomenclature A bed area (m 2 ) E(t) RTD curve (-) ε bed porosity (-) F dry basis solid flow rate (kg/h) f falling rate drying factor ( • C) G dry basis gas flow rate (kg/h) h bed height (m) L total length of dryer (m) m B mass of bed (kg) N V local solids dying rate (kg/h/m 2 ) NTU number of transfer units (-) Nu nusselt number (-) Pe Peclet number (-)Pr Prandtl number (-) Re p particle Reynolds number (-) T G local gas temperature ( • C) T GI initial gas temperature ( • C) T i inlet gas tenmperature ( • C) T o exhaust gas temperature ( • C) T S local solids temperature ( • C) T wb wet bulb temperature ( • C) t time (s) τ residence time (s) X dry basis solids moisture content (kg/kg) X i inle...

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“…Vibrations enhance drying rates due to de-agglomeration and the consequent increase of the specific evaporation area in gas-solid contact (Ivarez, Blasco, Gomez & Cubillos 2005;Pakowaski, Mujumdar & Strumillo 1984). A vibrated bed of particles to be dried along with multimode and intermittent heat input (Islam, Ho and Mujumdar 2003) by conduction and radiation under vacuum is proposed as a new strategy to improve the dehydration rate of solids in particulate form.…”

Section: Introductionmentioning

confidence: 98%

Combined Radiant and Conductive Vacuum Drying in a Vibrated Bed

Rahman¹,

Mujumdar²

2008

International Journal of Food Engineering

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Wet particles are often difficult to dry due to their stickiness and tendency to form lumps. Mechanical vibration can assist in separating such particles as well as in mixing beds of dissimilar particles if necessary. Delumping also exposes surfaces for evaporation. The objective of this experimental project is to design, build and test a laboratory size vibrated drum dryer under vacuum. The basic concept is to design a variable frequency, variable amplitude vibratory unit on which a horizontal drum is seated. An experimental approach was employed to permit simultaneous or individual mode of conduction and radiation heat input. Cube shaped potatoes and apples were used as model samples for experimental tests. Experiments were also performed using spherical shaped silica gel. Five different drying conditions were compared experimentally. These are: case-1, effect of vacuum; case-2, vacuum with vertical sinusoidal vibration (Amplitude: 0-5mm, frequency: 10-50 Hz); case-3, vacuum with vibration and conduction heat input (40C); case-4, vacuum with vibration and radiation heat input (1875 W/m2); case-5, vacuum using vibrating bed dryer with simultaneous conduction and radiation heat input. An energy savings strategy for drying is proposed based on the study. Results indicated that the proposed system is a variable option to reduce the process time under vacuum compared to other drying methods.

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A First Principles–Neural Networks Approach to Model a Vibrated Fluidized Bed Dryer: Simulations and Experimental Results

Cited by 18 publications

References 11 publications

Mathematical Modeling of a Continuous Vibrating Fluidized Bed Dryer for Grain

Mathematical Modeling of a Continuous Vibrating Fluidized Bed Dryer for Grain

Fluidized Bed Dryers — Recent Advances

Combined Radiant and Conductive Vacuum Drying in a Vibrated Bed

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