• Journal of Environmental Science International
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• v.3 no.1
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• pp.49-56
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• 1994

Effect of the liquid circulation velocity on the biofilm development was investigated in an inverse fluidized bed biofilm reactor(IFBBR). To observe the effect of the influent COD concentration on biofilm simultaneously, the influent COD value was adjusted to 1000mg/1 f for 1st reactor, and 2500mg/l for 2nd reactor. The liquid circulation velocity was adjusted by controlling the initial liquid height. As the liquid circulation velocity was decreased, the settling amount of biomass was increased and the amount of effluent biomass was decreased. Since the friction of liquid was decreased by the decrease of liquid circulation velocity, the biofilm thickness was increased and the biofilm dry density was decreased. In the 1st reactor the SCOD removal efficiency was constant regardless of the variation of the liquid circulation velocity, but it was increased by the decrease of the liquid circulation velocity because of more biomass population in 2nd reactor.

• Journal of environmental and Sanitary engineering
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• v.10 no.3
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• pp.1.1-15
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• 1995

This study was performed to estimate the characteristics of the organic wastewater treatment and bed porosity with the circulation velocity in the anaerobic fluidized bed biofilm reactor. The results were as follows; 1. With Increasing circulation velocity the fluidized bed expanded smooth and with increasing initial particle volume the fluidized bed was increased. 2. With increasing circulation velocity the gasproduction was increased, but at 1.Scnt/sec of circulation velocity AFBBR showed the highest value of methane production rate per removed COD. Therefore, for the purpose of economical operation in AFBBR, 1.5cm/sec of circulation velocity was optimum 3. The microorganisms were colonized in the crevice of the media. 4. On fluidization, COD, VA,55 profiles with the reactor height were not showed. In conclusion, AFBBR suit the organic wastewater treatment's purpose, and at 1.5cm/sec of circulation velocity the system is economical in an energy Point of view.

• Journal of Environmental Science International
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• v.5 no.1
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• pp.93-102
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• 1996

Hydrodynamic characteristics such as gas holdup, liquid circulation velocity and bed expansion in a hexagonal inverse fluidized bed were investigated using air-water system by changing the ratio ($A_d$/$A_r$) of cross-sectional area between the riser and the downcomer, the liquid level($H_1$/H), and the superficial gas velocity($U_g$). The gas holdup and the liquid circulation velocity were steadily increased with the superficial gas velocity increasing, but at high superficial gas velocity, some of gas bubbles were carried over to a downcomer and circulated through the column. When the superficial gas velocity was high, the $A_d$/$A_r$ ratio in the range of 1 to 2.4 did not affect the liquid circulation velocity, but the maximum bed expansion was obtained at $A_d$/$A_r$ ratio of 1.25. The liquid circulation velocity was expressed as a model equation below with variables of the cross-sectional area ratio($A_d$/$A_r$) between riser to downcomer, the liquid level($H_1$/H), the superficial gas velocity($U_g$), the sparser height[(H-$H_s$)/H], and the draft Plate level($H_b$/H). $U_{ld}$ = 11.62U_g^{0.75}$${(\frac{H_1}{H})}^{10.30}$${(\frac{A_d}{A_r})}^{-0.52}$${(\frac({H-H_s}{H})}^{0.91}$${(\frac{H_b}{H})}^{0.13}$

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.446-455
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• 2023

A mathematical model for predicting the liquid circulation velocity in an airlift reactor was developed based on the mechanical energy balance of the fluid circulation loop. The model considered the energy loss due to a 90° turn, the energy loss due to friction, and the energy loss due to the change in cross-sectional area at each part of the reactor. The model that separately considered the loss coefficients related to friction, direction change, and cross-sectional area change was able to predict the liquid circulation velocity better than the previous model using lumped parameters. The liquid circulation velocity was measured by the tracer pulse method. Most of our experimental results obtained in external-loop airlift reactors, which had the top and bottom connecting pipes, as well as other investigators' results obtained in various types of airlift reactors, were well predicted by the developed model with an error within 20%. Useful empirical equations for the loss coefficient related to the 90° turn of the circulating fluid were obtained in external and internal-loop airlift reactors and used to predict the liquid circulation velocity.

• KSBB Journal
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• v.7 no.1
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• pp.59-65
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• 1992

Hydrodynamics and mixing characteristics such as circulation time, mixing time, circulation velocity and axial dispersion coefficient were investigated using highly viscous pseudoplastic solutions of carboxymethyl cellulose(CMC) in an external circulation loop air-lift reactor with 13$\ell$ working volume. The superficial gas velocity was changed from 1.9 to 6.2cm/s and CMC concentration from 0 to 1.0wt%. The theoretical model based on the pressure balance is developed mathematically to predict liquid circulation velocity. Gas hold-up, circulation velocity and axial dispersion coefficient of liquid phase increased with increasing gas velocity and decreased slightly with increasing liquid viscosity. Mixing time and circulation time decreased with increasing gas velocity and increased with increasing liquid viscosity. Experimental data on liquid circulation velocity were in good agreement with the predicted values.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.6
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• pp.635-641
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• 2018

To select the operating condition of 0.5 MWth chemical looping combustion system, minimum fluidization velocity, transition velocity to fast fluidization and solid circulation rate were measured using mass produced new oxygen carrier (N016-R4) which produced by spray drying method for 0.5 MWth chemical looping combustion system. A minimum fluidization velocity decreased as the pressure increased. The measured transition velocity to fast fluidization was 2.0 m/s at ambient temperature and pressure. The measured solid circulation rate increased as the solid control valve opening increased. We could control the solid circulation rate from 26 to $93kg/m^2s$. Based on the measured minimum fluidization velocity and transition velocity to fast fluidization, we choose appropriate operating conditions and demonstrated continuous solid circulation at high pressure condition (5 bar-abs) up to 24 hours.

• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.311-317
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• 2015

It is difficulty to calculate velocity circulation in centrifugal pump impeller outlet accurately. Velocity circulations of a double-blade pump impeller outlet were calculated with Stodola formula, Weisner formula and Stechkin formula. Simultaneously, the internal flow of impeller for the double-blade pump were measured with PIV technology and average velocity circulations at the 0.8, 1.0 and 1.2 times of design flow were obtained. All the experimental values were compared with the above calculation values at the three conditions. The results show that calculation values of velocity circulations with Weisner formula is close to the experimental values. On the basis of the above, velocity circulations of impeller outlet were corrected. The results of experimental verification show that the corrected calculation errors, whose maximum error is 3.65%, are greatly reduced than the uncorrected calculation errors. The research results could provide good references for establishment of theoretical head and multi-condition hydraulic optimization of double-blade pumps.

• Journal of Power System Engineering
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• v.3 no.2
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• pp.13-19
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• 1999

The purpose of the present experimental study is to apply multi-point simultaneous measurement by PIV(Particle Image Velocimetry) to high-speed flow region within a domestic boiler circulation pump. Two different kinds of flow rate($27{\ell}/min,\;19{\ell}/min$)are selected as experimental condition. A volute casing and Impeller made of transparent Polycarbonate were made for the easy access of the illumination laser via fiber optical line and cylinder lens assembly to the measuring region. A CCD camera is syncronized with AOM to acquire clear original particle images. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. The instantaneous and time-mean velocity distribution, velocity profile and kinetic energy are represented quantitatively at the full-scale region for the deeper understanding of the unsteady flow characteristics in a commercial circulation pump.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.459-467
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• 2006

In this study, hydraulic and numerical model experiments were performed to analyze and improve the effects of flow-rate increase in the intake canal of Boryeong Thermal Power Plants on the flow condition in the circulation water pump (CWP) chambers. Based on the numerical simulation results, when the flow-rate increased in the circulation water intake canal, the velocity in the canal and vertical vorticities in the circulation water pump chambers increased and hence the vortex occurrence potential would be greatly increased. It was found by performing hydraulic model experiments that the velocity distribution near the bottom in the inlet of the circulation water pump chambers was highly non-uniform while the velocity distribution near the water surface was nearly uniform. To reduce the non-uniformity in the velocity distribution, triangular flow deflectors were devised. The installation of the flow deflectors in the inlet of circulation water pump chambers was successfully to reduce velocity non-uniformities and to remove flow reversal problems.

• Journal of Environmental Science International
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• v.20 no.6
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• pp.679-686
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• 2011

The characteristics of circulation in the coastal area of Jeju Harbor in Korea was examined using the Princeton Ocean Model(POM) with a sigma coordinate system. The result of numerical analysis well corresponded to the observed current data. The velocity at offshore was stronger compared to coastal area during the both period of in maximum flood and maximum ebb of spring tide. According to mean wind velocity, the tidal velocity at the shallow area of Jocheon was slightly increasing during maximum ebb. The effect of wind on the circulation was stronger in shallow area and showed rapid change with depth.