• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2008.04a
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• pp.101-108
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• 2008

Polymer electrolyte membrane (PEM) fuel cells are promising power generation devices which are ideal for residential and automobile applications, thanks to their fast transient characteristics. However, liquid water produced in PEM fuel cells should be properly managed to enhance the performances and durabilities of the cells. In this study, a visualization experiment was conducted to investigate the flow behavior of water droplets in cathode channels. The visualization experiment was done with four different model flow channels which were made by varying the material (Acrylic and Teflon) and the channel width (1 mm and 2 mm). Acrylic is hydrophilic (contact angle is about $80^{\circ}$) while Teflon is hydrophobic (contact angle is about $120^{\circ}$). A computational fluid dynamics (CFD) analysis was also performed to compare the observed and the simulated two-phase water/air flow characteristics in cathode channels. The computational models were made to be consistent with the geometries and surface properties of the model flow channels. Both the experimental and numerical results showed that the Teflon cathode channel with 1 mm width has the best water management performance among four model flow channels considered. A close correlation was found between the experimental visualization results and the numerical CFD simulation results.

• Journal of the Korean Society of Visualization
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• v.17 no.2
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• pp.73-82
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• 2019

The subsurface vortex - which occurs inside the cylindrical sump - was visualized through Computational Fluid Dynamics (CFD) and experiment. The analysis of subsurface vortex inside the cylindrical sump was already carried out using CFD techniques by the first author. To understand the subsurface vortex more clearly, an experimental analysis was carried out with a 1/5th scale model; and the flow rate was calculated according to the similarity law. The experimental results of vortex visualization matches well with the CFD results. The surface roughness model and Anti Vortex Device (AVD) model have been investigated to control the subsurface vortex. For the case of average surface roughness of 1mm and 5mm, the subsurface vortex appears and the vorticity is higher when compared to that of a smooth surface condition. However, for the AVD model, the subsurface vortex is completely removed and the internal flow is stabilized.

• Journal of the Korean Society of Visualization
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• v.21 no.3
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• pp.49-56
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• 2023

The Polymer electrolyte membrane fuel cell (PEMFC) operates at ambient temperature as a low-temperature fuel cell. During its operation, voltage losses arise due to factors such as operating conditions and material properties, effecting its performance. Computational simulations of fuel cells can be categorized into 1D simulation and CFD, chosen based on their specific application purposes. In this study, we carried out an analysis validation using 1D geometry and compared its performance with the results from 2D geometry analysis. CFD allows for the representation of pressure, velocity distribution, and fuel mass fraction according to the geometry, enabling the analysis of current density. However, the 1D simulation, simplifying governing equations to reduce time cost, failed to accurately account for fuel distribution and changes in fuel concentration due to fuel cell operations. As a result, it showed unrealistic results in the cell voltage region dominated by concentration loss compared to CFD.

• Journal of the Korean Society of Visualization
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• v.15 no.3
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• pp.34-40
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• 2017

Within fractionating devices existing in separation and purification industries, sieve trays are widely used as tower internals and their choice is due to economical attractiveness. While operating a trayed distillation tower weeping phenomenon has a critical effect on the efficiency, in this case study a weeping phenomenon was undertaken by means of numerical model in a rectangular sieve tray. Eulerian-Eulerian Computational Fluid Dynamics (CFD) method was used and the obtained CFD results are in a good agreement with the experimental data in terms of weeping rate and pressure drop.

• International Journal of Safety
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• v.11 no.2
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• pp.5-9
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• 2012

The discharge properties of super high-pressure mercury lamp are due to resistance heating for energy input, and results in temperature increase. The cooling equilibrium state is reached by the heat conduction, convection and radiation. In order to predict the fluid flow and heat transfer in and around the mercury lamp accurately, its visualization is of utmost importance. Such visualization is carried out by CFD program in this study. We focus on Anode shape to calculate four cases, namely AA, AB, AC and AD separately, and compare the temperature distribution and velocity vector in each case to predict cooling capacity and fluid flow properties. It can be concluded that the shape of anode plays an important role that affects the fluid flow and heat transfer in a mercury lamp.

• Journal of the Korean Society of Visualization
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• v.10 no.1
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• pp.55-59
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• 2012

Reverse Design(RD) plays an important role in simulation engineering, such as CFD (Computational Fluid Dynamics) and Virtual Engineering and Design. RD becomes much more valuable when there is no shape data of the practical models for CFD grid generations. In this study, two-camera based rapid prototyping(RP) system is proposed. 3D-PTV based measurement algorithm was adopted. The developed system was applied to reconstruct three-dimensional data of a human face, a motorcycle model, a cylindrical body and a triangular pyramid.

• Journal of the Korean Society of Visualization
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• v.17 no.2
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• pp.67-72
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• 2019

In this study, we investigate the non-reacting and reacting performance of single nozzle for post H class gas turbine by using commercial CFD tool, CONVERGE, based on adaptive mesh refinement. By varying swirl number and mixing length of base nozzle design. Through the numerical analysis, basic phenomena can be well described with respect to fuel concentration for non-reacting flow, temperature distribution, velocity vector and combustion outlet temperature distribution for reacting flow. However, there are rooms for improvements in model accuracy by comparing test results. Comparison between numerical analysis are planning for further study.

• Journal of the Korean Society of Visualization
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• v.21 no.2
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• pp.55-62
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• 2023

The characteristic of jet impinging on the concave surface were analyzed through thermographic phosphor thermometry (TPT) and numerical investigation. Under a jet Reynolds number of 6600, nozzle diameters and nozzle-to-surface distances (H/d) were changed 5mm and 10mm and H/d=2 and 5. The RNG k-ε turbulence model can accurately predict the distribution of Nusselt number, compared to other models (SST k-ω, realizable k-ε). Heat transfer characteristics varied with the nozzle diameter and H/d, with a secondary peak noted at H/d =2, due to vortex-induced flow detachment and reattachment. An increase in nozzle diameter enhanced jet momentum, turbulence strength, and heat transfer.

• Journal of the Korean Society of Visualization
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• v.9 no.4
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• pp.28-34
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• 2011

A volumetric gear pump is often used in extensive industrial applications to provide both high pressure and sufficiently high flow rate by physical displacement of finite volume of fluid with each revolution. Template mesh function in commercial CFD software, PumpLinx, by which 3-D meshes in the complex region between rotor and housing can be readily generated was employed for 3-D flow simulations. For cavitation analysis full cavitation model was included in 3-D simulations. The results showed high pulsation in pressure and flowrate which is implicated in pump vibration and noise. A model test for cavitation visualization was conducted and the results showed good qualitative agreement with numerical prediction.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.702-707
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• 2001

The characteristics of flow in dividing regions are precise, therefore their classification is very important not only in industry but also in hydrodynamics. By now, many studies of flow in dividing regions have been performed, but flow characteristics that use visualization in dividing regions have not been studied. The present study of the PIV and the CFD exhibit average velocity distributions, kinetic energy distributions and total pressure distributions etc of the total flow field due to the development of the accurate visualization optical laser and of optical equipment. Also, PIV is accurate with the flows characteristics of the dividing region as continuous analysis is done using input equipment. The study analyzes average velocity vector field, average kinetic energy, x-axis stress distributions, average and total pressure distributions of dividing regions with flow for visualization of the PIV and the CFD measurement in a dividing rectangular duct.