Investigation of  the regularities of vortical flows in a cyclone-bed chamber

Experimental investigation of the radial distributions of tangential and longitudinal velocities, total and static pressures in the vortex zone of a cyclone-bed chamber of diameter 0.21 m has been carried out. The experiments were carried out at various regime parameters (fraction of bottom blast, total air volume flow) and geometric parameters (diameter and shape of the outlet) of the chamber, and also in the presence of a fixed or fluidized bed of granular material. The influence of nonisotherm of bottom and tangential blast on the distribution pattern of velocity and pressure in the vortex zone of the cyclone-bed chamber is investigated. There was determined the influence of bottom blast temperature on the longitudinal velocity of air in the central part of the vortex zone chamber. It is shown that the diameter of the outlet has a significant effect on the pressure in the chamber. The longitudinal velocity in the central part of the chamber is practically independent of the shape of the outlet. The presence of the fluidized bed has an effect on the hydrodynamics of the cyclone-bed chamber vortex zone. In the presence of the fluidized bed there has been a violation of the self-similarity of hydrodynamic dimensionless parameters distribution in the vortex zone. The obtained experimental data were summarized within the framework of the similarity theory with the use of a dimensionless quantity characterizing the hydrodynamics of an inhomogeneous fluidized bed – the Froude number (Fr). The use of the Froude number makes it possible to take into account the effect of the fluidized bed hydrodynamics on the features of air velocity and pressure distributions in the vortex zone, and also takes into account the influence of such an important factor as the fraction of bottom blast.

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Study of Radial Wall Jets from Ceiling Diffusers at Variable Air Volume

Energies ◽

10.3390/en14010240 ◽

2021 ◽

Vol 14 (1) ◽

pp. 240

Author(s):

Maria Hurnik ◽

Jan Kaczmarczyk ◽

Zbigniew Popiolek

Keyword(s):

Velocity Distribution ◽

The Self ◽

Air Velocity ◽

Self Similarity ◽

Wall Jets ◽

Radial Wall ◽

Variable Air Volume ◽

Air Volume ◽

Terminal Zone ◽

The Mean

The knowledge of the air velocity distribution in the supply jets is essential when designing ventilation and air conditioning systems. In this study, we tested and analyzed the velocity distributions in the radial wall jets—these jets are commonly used in ventilated rooms. Tests included jets from two ceiling diffusers of different constructions, at three airflow rates. The mean air speed distributions were measured with a 16-channel hot-sphere anemometer both in the self-similarity zone and in the terminal zone. A specially developed method of converting the mean speed to mean velocity was used. The measurement results show that the spread coefficients of the jets from both diffusers were the same, but the positions of the virtual origin were different. Due to the friction of the jet with the ceiling and the transfer of momentum to the recirculating flows, the momentum flux in the self-similarity zone decreased by up to 50%. An improved method for calculating velocity distributions in radial wall jets was developed and validated. This method takes into account the decrease of momentum, non-zero position of the jet origin, and faster velocity decrease in the terminal zone. A reliable method of predicting air velocity distribution in radial wall jets (RWJs) from ceiling diffusers may allow to properly select the diffuser size, its location, and the range of flow rate changes. The design process for variable air volume systems can be facilitated.

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Construction Ventilation Scheme Optimization of Underground Main Powerhouse Based on CFD

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.368-370.619 ◽

2013 ◽

Vol 368-370 ◽

pp. 619-623

Author(s):

Zhen Liu ◽

Xiao Ling Wang ◽

Ai Li Zhang

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Flow Field ◽

Air Flow ◽

Scheme Optimization ◽

Pressure Distributions ◽

Air Volume ◽

Computational Fluid Dynamics Cfd ◽

Traditional Construction ◽

Ventilation Scheme

For the purpose of avoiding the deficiency of the traditional construction ventilation, the ventilation of the underground main powerhouse is simulated by the computational fluid dynamics (CFD) to optimize ventilation parameters. A 3D unsteady RNG k-ε model is performed for construction ventilation in the underground main powerhouse. The air-flow field and CO diffusion in the main powerhouse are simulated and analyzed. The two construction ventilation schemes are modelled for the main powerhouse. The optimized ventilation scheme is obtained by comparing the air volume and pressure distributions of the different ventilation schemes.

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Drying behavior, diffusion modeling of cuminum cyminum L. undergoing microwave-assisted fluidized bed drying

Proceedings of 21th International Drying Symposium ◽

10.4995/ids2018.2018.7406 ◽

2018 ◽

Author(s):

Gholamreza Askari ◽

Atefe Babaki ◽

Zahra Emamdjomeh

Keyword(s):

Fluidized Bed ◽

Effective Diffusivity ◽

Air Velocity ◽

Cuminum Cyminum ◽

Fluidized Bed Dryer ◽

Microwave Assisted ◽

Air Temperatures ◽

Drying Behavior ◽

Fluidized Bed Drying ◽

Kinetics Of

In order to conserve cuminum cyminum L. during long storage periods, the drying kinetics of this seed undergoing microwave-assisted fluidized bed dryer at various microwave output power (300, 600 and 900w), air velocity (10, 15 and 20 m/s) and air temperatures (45, 55 and 65ᵒc) were studied. The main aim of this research is developing a mathematical model of mass transfer to investigate the microwave-assisted fluidized bed drying of cuminum cyminum L. seed. In this paper, we tried to discover a good model to evaluate moisture effective diffusivity (Deff). Keywords: cuminum cyminum L, microwave-assisted drying, mathematical modeling,

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Comparison on Simulation and Experiment of Supply Air through Metro Vehicle Air Conditioning Duct

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.44-47.1724 ◽

2010 ◽

Vol 44-47 ◽

pp. 1724-1728

Author(s):

Hong Ge Tao ◽

Huan Xin Chen ◽

Jun Long Xie ◽

Jun Zhi Jiang

Keyword(s):

Air Conditioning ◽

Optimization Design ◽

Simulation Method ◽

Test Results ◽

Air Velocity ◽

Relative Deviation ◽

Air Volume ◽

Experiment Validation ◽

Simulation And Experiment ◽

Actual Test

CFD technique is often employed to simulate and optimize air duct design, but the corresponding experiment validation in metro vehicle is rare. By taking an independent metro vehicle duct as research object in this paper, supply air through air duct is simulated and compared with the actual test results from the angle of supply air velocity at each outlet and supply air volume through several outlets of air duct. The results show that the relative deviation of simulation and test value of air velocity at most of the outlets are within or near ±20%, which is acceptable for the engineering applications. Moreover, the ratio of supply air volume through several outlets to the corresponding total supply air volume through main air duct or flat duct in the case of simulation is consistent with that in the case of experiment. It can be concluded that numerical simulation method is effective and reliable in air duct optimization design of metro vehicle.

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Fluidized bed bubbles and Froude number

Chemical Engineering Science ◽

10.1016/0009-2509(76)80066-8 ◽

1976 ◽

Vol 31 (9) ◽

pp. 852 ◽

Cited By ~ 3

Author(s):

N. Epstein

Keyword(s):

Froude Number ◽

Fluidized Bed

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Effect of Biodegradable Binder Properties and Operating Conditions on Growth of Urea Particles in a Fluidized Bed Granulator

Materials ◽

10.3390/ma12142320 ◽

2019 ◽

Vol 12 (14) ◽

pp. 2320 ◽

Cited By ~ 1

Author(s):

Ehsan Zhalehrajabi ◽

Kok Keong Lau ◽

Ku Zilati Ku Shaari ◽

Seyed Mojib Zahraee ◽

Seyed Hadi Seyedin ◽

...

Keyword(s):

Fluidized Bed ◽

Air Temperature ◽

Scale Up ◽

Cost Effective ◽

Stokes Number ◽

Operating Conditions ◽

Air Velocity ◽

Air Inlet ◽

Lower Temperature ◽

Penetration Time

Granulation is an important step during the production of urea granules. Most of the commercial binders used for granulation are toxic and non-biodegradable. In this study, a fully biodegradable and cost-effective starch-based binder is used for urea granulation in a fluidized bed granulator. The effect of binder properties such as viscosity, surface tension, contact angle, penetration time, and liquid bridge bonding force on granulation performance is studied. In addition, the effect of fluidized bed process parameters such as fluidizing air inlet velocity, air temperature, weight of primary urea particles, binder spray rate, and binder concentration is also evaluated using response surface methodology. Based on the results, binder with higher concentration demonstrates higher viscosity and higher penetration time that potentially enhance the granulation performance. The viscous Stokes number for binder with higher concentration is lower than critical Stokes number that increases coalescence rate. Higher viscosity and lower restitution coefficient of urea particles result in elastic losses and subsequent successful coalescence. Statistical analysis indicate that air velocity, air temperature, and weight of primary urea particles have major effects on granulation performance. Higher air velocity increases probability of collision, whereby lower temperature prevents binder to be dried up prior to collision. Findings of this study can be useful for process scale-up and industrial application.

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Investigation of Ash-Related Issues During Combustion of Maize Straw and Wood Biomass Blends in Lab-Scale Bubbling Fluidized Bed Reactor

Journal of Energy Resources Technology ◽

10.1115/1.4044221 ◽

2019 ◽

Vol 142 (2) ◽

Cited By ~ 1

Author(s):

Krzysztof Głód ◽

Janusz Lasek ◽

Krzysztof Słowik ◽

Jarosław Zuwała ◽

Daniel Nabagło ◽

...

Keyword(s):

Fluidized Bed ◽

Air Velocity ◽

Interesting Phenomenon ◽

Simultaneous Application ◽

Agglomeration Process ◽

Bubbling Fluidized Bed ◽

Bed Agglomeration ◽

The Cost ◽

The Impact ◽

Combustion Of Solid Fuels

Abstract During the combustion of solid fuels, the undesired effects of ash transformation include bed agglomeration, slagging, and fouling processes. In particular, a problematic consequence of bed agglomeration is the defluidization process, resulting from the disappearance of gaseous bubbles that are created behind air distributors. Different solutions can be applied against the agglomeration process. One possible method is to apply some additives that influence the ash behavior, thus inhibiting the agglomeration process. This paper presents the results of investigations into ash-related issues in a laboratory-scale bubbling fluidized bed (BFB) reactor. In particular, the impact of additives (kaolin, halloysite, fly ash, and the residuals from wet desulfurization system (IMOS)) on bed agglomeration was investigated. It was found that the addition of these compounds increased the defluidization time from ∼109 min (without additive) to ∼285 min in the BFB (with the addition of 0.1 g/min of kaolin). The morphology of additive (kaolin and halloysite) transformation after their addition into the combustion chamber was discussed. Another interesting phenomenon is that residuals from the IMOS exhibited the ability to be an additive against the agglomeration process. The defluidization time can be also significantly increased by the simultaneous application of the additive and the control of fluidization air velocity. The procedure of periodical bed moving by impulse primary air feeding against defluidization (PADM) is suggested and discussed. The PADM procedure resulted in a 36% reduction of additive, thus reducing the cost of measures against ash-related issues.

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Heat Exchange in Fluid-Dense Particle Moving Beds

Journal of Heat Transfer ◽

10.1115/1.3614316 ◽

1967 ◽

Vol 89 (1) ◽

pp. 1-6 ◽

Cited By ~ 7

Author(s):

L. E. Sissom ◽

T. W. Jackson

Keyword(s):

Heat Exchanger ◽

Volume Ratio ◽

Reynolds Numbers ◽

Effective Length ◽

Air Velocity ◽

Two Phase ◽

Dense Particle ◽

Pressure Distributions ◽

Constant Area ◽

Temperature And Pressure

The characteristics of nonisothermal two-phase steady flow in a vertical pipe of constant area were investigated experimentally. Temperature and pressure distributions were determined, and the void fraction was measured under flowing conditions. Aluminum granules of 0.027 in. mean diameter flowed with gravity while heated air was forced countercurrently to the solids flow. Reynolds numbers, based on the superficial air velocity, from 10 to 50 were investigated. The solids flow rate was varied from 472 to 18,900 lbm/hr-sq ft. Utilizing the regeneration principle, the effective length of a fluid-to-particle heat exchanger was determined. Its small value and the large surface area to volume ratio (2980 sq ft/cu ft) indicate that such a heat exchanger would be very compact.

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