• Journal of Korea Water Resources Association
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• v.34 no.6
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• pp.725-733
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• 2001

In this study, variation of effluent of residual chlorine concentration was estimated from bench scale distribution reservoir test according to variation of flow and baffle condition. According to the bench scale test results, when the flow rate was an unsteady state, difference between the case of no-baffle in the reservoir and the case of two-baffles in the reservoir became less than the condition when the effluent flow was in a steady state. Consequently, the results are caused by the flow rate variation. Thus, the baffle is less effective than a clearwell of steady state condition.

• Journal of Environmental Science International
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• v.22 no.9
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• pp.1131-1139
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• 2013

Desorption characteristics of VOCs were investigated for the effective recovery of gasoline vapor. The adsorption capacity and desorption capacity were excellent at relatively low temperatures. The differences in the desorption capacity were not large in the condition; desorption temperature $25^{\circ}C$, desorption pressure 760 mmHg, inlet air flow rate 0.5 L/min, but were relatively great in the condition; desorption temperature $0^{\circ}C$, desorption pressure 60 mmHg, inlet air flow rate 1.0 L/min. The desorption ability of pentane was increased to about 81.4%, and the desorption ability of hexane was increased to about 102%, also the desorption ability of toluene was increased to about 156.7% by changes of temperature, pressure, inlet air flow rate in the experimental conditions. The optimum desorption condition for the effective recovery of VOCs was in the conditions; desorption temperature $0^{\circ}C$, desorption pressure 60 mmHg, inlet air flow rate 1.0 L/min.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.63-68
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• 2014

The numerical analysis of fluid flow in the tube cleaning system is examined. The working flow used in this study is seawater, and the temperature change is not considered as the temperature change of seawater in the tube cleaning system is negligible. Also, the analysis is performed under the assumption of steady state. The screens of complicated morphologies are simplified for the analysis, and only one fourth of the tube cleaning system is modeled as the system has a symmetrical shape. The velocity inlet boundary condition is employed for the seawater inlet, whereas the outflow boundary condition is employed for two seawater outlets. In applying the outflow boundary condition for the system with more than two outlets, the flow rate can be arbitrarily assigned. In the analysis, the finite-volume method based numerical analysis tool, the pressure based solver, the standard k-$\varepsilon$ model are utilized, and the under relaxation factor is modified appropriately. From the analysis, the distribution of velocity vectors, pressure and path lines are obtained, and the physical characteristics of fluid flow in the tube cleaning system is well-examined.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.342-350
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• 1995

To determine the factors which affect the flow of dentinal fluid through cat dentinal tubules in vivo, the flow of fluid was measured by observing the movement of the fat droplets of dilute milk in a glass capillary with a microscope connected to the monitor. After measuring the exposed area of dentin, hydraulic conductances of dentin were calculated. The mean pressure which stoped the outward flow of dentinal fluid was 9.5mmHg. The hydraulic conductance of dentin under the condition of pulp exposed was increased by 21 % from that under the condition of dentin exposed. Under the conditions of pulp cut and pulp removed, the hydraulic conductances of dentin were increased by 22 % and 31 % respectively from that under the condition of dentin exposed. These results show that the direction and rate of dentinal fluid flow in cat dentin is affected mainly by the hydrostatic pressure of interstitial fluid of pulp tissue in the state of low compliance. Both of the osmotic effect produced by the protein constituents of interstitial fluid across the odontoblast tell layer and the change of interstitial fluid pressure produced by the state of the microcirculation of the pulp also affect the direction and rate of dentinal fluid in some degree.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.3 s.258
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• pp.292-299
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• 2007

In gas turbine technology, the flame stability is inherently greater in conventional diffusion type combustion over a wider range fuel to oxidizer ratio. However, premixed type combustion which has narrow flame stability region, is widely used due to environmental reason. It has been observed in experiments that combustion instability of low frequency (${\sim}10Hz$) results from the modulation of equivalence ratio at fuel injection hole when a pressure fluctuation propagates upwards along the channel of the burner under an unchoked fuel flow condition. In this study, a commercial program was used to determine how the fuel flow rate changed with respect to the pressure, velocity of the fuel flow and the mass fraction in a choked and an unchoked condition. The calculation focuses on the upstream of the dump plane to know how the forced pressure with the fuel injection conditions affects the modulation of the equivalence ratio. Therefore, it is found that pressure fluctuation leads to oscillation of mass flow rate and then results in equivalence ratio modulation under the unchoked fuel flow condition.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.17-23
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• 2007

In the present work, flow analysis has been performed in the steam turbine bypass control valve (single-path type) for two different cases i.e., case with steam only and case with both steam and water. The numerical analysis is performed by solving three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations. The shear stress transport (SST) model and $k-{\varepsilon}$ model are used to each different case as turbulence closure. Symmetry condition is applied at the mid plane of the valve while adiabatic condition is used at the outer wall of the cage. Grid independency test is performed to find the optimal number of grid points. The pressure and temperature distributions on the outer wall of the cage are analyzed. The mass flow rate at maximum plug opening condition is compared with the designed mass flow rate. The numerical analysis of multiphase mixing flow(liquid and vapor) is also performed to inspect liquid-vapor volume fraction of bypass valve. The result of volume fraction is useful to estimate both the safety and confidence of valve design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.733-743
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• 2000

We solve the integral representation of the Navier-Stokes equations in a lagrangian view by tracking the particles, which have vortex strengths. We simulate the unsteady viscous flow around an impulsively started cylinder using the vortex particle method. Particles are advanced via the Biot-Savart law for a lagrangian evolution of particles. The particle strength is modified based on the scheme of particle strength exchange. The solid boundary satisfies the no-slip boundary condition by the vorticity generation algorithm. We newly modify the diffusion scheme and the boundary condition for simulating an unsteady flow efficiently. To save the computation time, we propose the mixed scheme of particle strength exchange and core expansion. We also use a lot of panels to ignore the curvature of the cylinder, and not to solve the evaluation of the surface density. Results are compared to those from other theoretical and experimental works.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.881-888
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• 2017

In general, the choking phenomenon occurs by flow acceleration for a turbine at high pressure ratio condition. In choking condition, total pressure ratio increases without mass flow rate variation. It is hard to predict choking characteristics by using conventional meanline analysis which used mass flow inlet boundary condition. In the present study, the algorithm for predicting choking point is developed to solve the problem. Moreover, performance estimation algorithm after choking is presented by reflecting the flow behaviour of flow expansion at choked nozzle or rotor. The analysis results are compared with 3D CFD analysis and experimental data to validate present method.

• Journal of Korea Water Resources Association
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• v.43 no.1
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• pp.41-49
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• 2010

Stepped weir of this study was suggested a type of natural type structures. Unique flow, such as Wave type flow, at downstream of mild slope stepped occurs. WTF(Wave type flow) is different with hydraulic jump occurred at Round crest weir. WTF is phenomenon to rise the water level by recirculation area occurred by step height at downstream of mild slope stepped. Wave height of WTF condition is higher than tailwater level and maximum velocity of WTF condition occurs in area of water surface. In this results, WTF presents to be important factor for design of join area of weir with levee. This study got and analyzed hydraulic condition occurred of WTF, scales of WTF and velocity profiles on flow patterns using experiments. WTF was not consider to stepped weir design and this results can be important data for design of stepped weir and structures.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.51-58
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• 2008

Many researches for effects of different flow configurations on performance of Proton Exchange Membrane Fuel Cell have extensively been done but the effects of flow direction at the same flow channel shape should be considered for optimal operation of fuel cell as well. In this paper a numerical computational methode for simulating entire reactive flow fields including anode and cathode flow has been developed and the effects of different flow direction at parallel flow was studied. Pressure drop along the flow channel and density distribution of reactant and products and water transport, ion conductivity across the membrane and I-V performance are compared in terms of flow directions(co-flow or counter-flow) using above numerical simulation method. The results show that the performance under counter-flow condition is superior to that under co-flow condition due to higher reactant and water transport resulting to higher ion conductivity of membrane.