Heat transfer and flow pattern in vertical liquid–solids flow

Garić‐Grulović, Radmila; Grbavčić, Željko; Arsenijević, Zorana

doi:10.1016/j.powtec.2004.07.006

Cited by 12 publications

(15 citation statements)

References 15 publications

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“…Moreover, it was observed that the frequency of particle-wall collisions decreases with increasing upward particle velocity, which is in accordance with our results as shown in Figure 9. At lower collision frequency at higher circulation rates was also reported by Garić-Grulović et al (2004) for 5 mm glass spheres in a rectangular fluidized bed of 60 × 8 mm 2 . At low-circulation rate the particles move vertically with some radial movement, but at higher circulation rates the particles follow vertical streamlines resulting in less particle-wall collisions.…”

Section: Collision Patterns Of Particlessupporting

confidence: 71%

Numerical and experimental analyses of anti‐fouling and heat transfer in the heat exchanger with circulating fluidized bed

et al. 2011

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Fluidized bed type heat exchangers are known to increase the heat transfer and prevent the fouling. For proper design of circulating fluidized bed heat exchanger it is important to know the effect of design and operating parameters on the bed to the wall heat transfer coefficient. The numerical analysis by using CFX 11.0 commercial code was done for proper design of the heat exchanger. The present experimental studies were also conducted to investigate the effects of circulating solid particles on the characteristics of fluid flow, heat transfer, and cleaning effect in the fluidized bed vertical shell and tube type heat exchanger with counterflow, at which a variety of solid particles such as glass (3 mmØ), aluminum (2-3 mmØ), steel (2-2.5 mmØ), copper (2.5 mmØ), and sand (2-4 mmØ) were used in the fluidized bed with a smooth tube. Seven different solid particles have the same volume, and the effects of various parameters such as water flow rates, particle diameter, materials, and geometry were investigated. The present experimental and numerical results showed that the flow velocity range for collision of particles to the tube wall was higher with heavier density solid particles, and the increase in heat transfer was in the order of sand, copper, steel, aluminum, and glass. This behaviour might be attributed to the parameters such as surface roughness or particle heat capacity. Fouling examination using 25,500 ppm of ferric oxide (Fe 2 O 3 ) revealed that the tube inside wall is cleaned by a mild and continuous scouring action of fluidized solid particles. The fluidized solid particles not only keep the surface clean, but they also breakup the boundary layer improving the heat transfer coefficient even at low-fluid velocities.Leséchangeurs de chaleur de type lit fluidisé sont connus pour augmenter le transfert de chaleur et empêcher l'encrassement. Pour une conception adéquate d'unéchangeur de chaleurà lit fluidisé circulant, il est important de connaître l'effet de la conception et des paramètres de fonctionnement du lit sur le coefficient de transfert de chaleur sur la paroi. L'analyse numérique par l'utilisation du code commercial CFX 11.0 aété réalisée pour une conception adéquate de l'échangeur de chaleur. Les présentesétudes expérimentales ontégalementété réalisées pour analyser les effets de particules solides circulantes sur les caractéristiques du débit de fluide, du transfert de chaleur et de l'effet de nettoyage dans l'échangeur de chaleur de type verticalà calandreà lit fluidisé avec contre-courant, pour lesquels unéventail de particules solides comme le verre (3 mmØ), l'aluminium (2-3 mmØ), l'acier (2-2.5 mmØ), le cuivre (2.5 mmØ) et le sable (2-4 mmØ) aété utilisé dans le lit fluidisé avec un tube lisse. Sept particules solides différentes ont le même volume et les effets de divers paramètres comme les débits d'eau, le diamètre des particules, les matières et la géométrie ontété analysés. Les résultats expérimentaux et numériques actuels indiquent que la portée de la vitesse d'écoulement pour la co...

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Section: Collision Patterns Of Particlessupporting

confidence: 71%

Numerical and experimental analyses of anti‐fouling and heat transfer in the heat exchanger with circulating fluidized bed

et al. 2011

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“…and j H ¼ f w =2 ¼ 0:0395=Re 0:25 m ; 15000 < Re m < 32000 ð23Þ correlated by the vertical liquid-solids flow in our previous work [21]. These Eqs.…”

Section: Momentum and Heat Transfer In Vertical Liquid-solids Flow Anmentioning

confidence: 84%

“…In our previous work [21] criterion for regime designation in the hydraulic transport of coarse particles is present. It is parameter c derived from the steady state one-dimensional suspension momentum equation [21]: À dp dz…”

Section: Flow Regimementioning

confidence: 99%

See 1 more Smart Citation

Wall-to-bed heat transfer in vertical hydraulic transport and in particulate fluidized beds

Garić‐Grulović

Bošković‐Vragolović

Grbavčić

et al. 2008

International Journal of Heat and Mass Transfer

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“…Added solid particles can improve the heat transfer rate between a fluid flow and a solid surface by advection, and disturbing and thinning the laminar sub-layer in the wall vicinity. 8 Dispersed particles would improve turbulence intensity of a flow up to 100% when their size is of the order of the turbulence length scale. 9 A theoretical study of local heat transfer enhancement through bombardment of a surface by spherical particles can be found in a paper by Murray.…”

Section: Introductionmentioning

confidence: 99%

Modeling of conductive particle motion in viscous medium affected by an electric field considering particle-electrode interactions and microdischarge phenomenon

2016

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Up and down motion of a spherical conductive particle in dielectric viscous fluid driven by a DC electric field between two parallel electrodes was investigated. A nonlinear differential equation, governing the particle dynamics, was derived, based on Newton's second law of mechanics, and solved numerically. All the pertaining dimensionless groups were extracted. In contrast to similar previous works, hydrodynamic interaction between the particle and the electrodes, as well as image electric forces, has been taken into account. Furthermore, the influence of the microdischarge produced between the electrodes and the approaching particle on the particle dynamics has been included in the model. The model results were compared with experimental data available in the literature, as well as with some additional experimental data obtained through the present study showing very good agreement. The results indicate that the wall hydrodynamic effect and the dielectric liquid ionic conductivity are very dominant factors determining the particle trajectory. A lower bound is derived for the charge transferred to the particle while rebounding from an electrode. It is found that the time and length scales of the post-microdischarge motion of the particle can be as small as microsecond and micrometer, respectively. The model is able to predict the so called settling/dwelling time phenomenon for the first time. Published by AIP Publishing. [http://dx

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Heat transfer and flow pattern in vertical liquid–solids flow

Cited by 12 publications

References 15 publications

Numerical and experimental analyses of anti‐fouling and heat transfer in the heat exchanger with circulating fluidized bed

Numerical and experimental analyses of anti‐fouling and heat transfer in the heat exchanger with circulating fluidized bed

Wall-to-bed heat transfer in vertical hydraulic transport and in particulate fluidized beds

Modeling of conductive particle motion in viscous medium affected by an electric field considering particle-electrode interactions and microdischarge phenomenon

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