• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.145-152
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• 2021

The purpose of this study was to determine the optimal distances between pipes to minimize the pressure loss and turbulent intensity. This was accomplished by investigating the distances between sleeve-jointed pipes and the flow changes in pipes based on variations in the Reynolds (Re) number when installing adjusting pieces for the pipes. When the thickness tp of the sleeve-jointed piping was fixed at 5 mm and the pipe lengths Lp were 10, 50, 100, and 200 mm, the correlations with the velocity of the sleeve-jointed part, pressure distribution, length of the reattachment point in the recirculation area, and Re number were analyzed. The flow characteristic of the sleeve-jointed part from a laminar to a turbulent flow region was determined by setting the Re range to 200 ≤ Re ≤ 5,000. This was done by utilizing Ansys Fluent 18.1, which is a commercial program. The enlargement and contraction ratios of the sleeve-jointed part were 1.2 and 0.83, respectively, and the turbulent intensity of the sleeve downstream edge and pressure change both increased as the Re number increased while Lp remained constant. The fact that the flow on the sleeve wall surface was disturbed by tp resulted in losses in velocity energy. Therefore, the edge of the sleeve-jointed part was also effected. When Lp was 10 mm or less, the turbulent intensity of the edge part did not change significantly as the Re number increased. The reattachment point in the recirculation area did not appear at Lp of 10 mm or less and was not affected by the vortex. In the case of 3,000 ≤ Re, the reattachment length of the wall surface of the sleeve-jointed part was nearly constant as Lp increased.

• Clean Technology
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• v.28 no.4
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• pp.316-322
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• 2022

The flow pattern at the inlet of the catalyst layer in a selective catalytic reduction (SCR) system is one of the key parameters influencing the performance of the denitrification process. In the curved diffusing parts between the ammonia injection grids and the catalyst layers, guide vanes are installed to improve flow uniformity. In the present study, a numerical simulation has been performed to investigate the effect of the geometrical configuration of the guide vanes on the aerodynamic characteristics of a denitrification facility. This application has been made to the existing SCR process in a large-scaled coal-fired power plant. The flow domain to be solved covers the whole region of the flow passages from the exit of the ammonia injection gun to the exit of the catalyst layers. ANSYS-Fluent was used to calculate the three-dimensional steady viscous flow fields with the proper turbulence model fitted to the flow characteristics. The root mean square of velocity and the pressure drop inside the flow passages were chosen as the key performance parameters. Four types of guides vanes were proposed to improve the flow quality compared to the current configuration. The numerical results showed that the type 4 configuration was the most effective at improving the aerodynamic performance in terms of flow uniformity and pressure loss.

• Clean Technology
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• v.29 no.4
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• pp.305-312
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• 2023

Due to the strengthening of environmental requirements, aging denitrification facilities need to improve their performance. The present study aims to suggest the possibility of improving performance using computational analysis techniques. This involved modifying both the geometric design and the operating conditions, including the flow path shape of the equipment such as the inlet guide vane and the curved diffusing part, and the flow control of the ammonia injection nozzle. The conditions presented in this study were compared with existing operating conditions in terms of the flow uniformity, the NH₃/NO molar ratio of the mixed gas flowing into the catalyst layer, and the total pressure drop of the facility. The flow field applied in the computational analysis ranged from the outlet of the economizer in the combustion furnace to the inlet of the air preheater, the full domain of the denitrification facility. The performances were derived by solving the flow fields using ANSYS-Fluent and the injection amount of ammonia was adjusted for each nozzle using Design Xplorer. Compared to the denitrification performances of the equipment currently in operation, the conditions proposed in this study showed an improvement in the flow uniformity and NH₃/NO composition ratio by 45.1% and 8.7%, respectively, but the total pressure drop increased by 1.24%.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1170-1179
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• 2009

The purpose of this work is to predict the low frequency aero-acoustic noise generated from the horizontal axis wind turbine, NREL Phase VI for the whole operating conditions of various wind speeds using large eddy simulation and Ffowcs-Williams and Hawkings model provided in the commercial code, FLUENT. Because there is no experimental data about wind turbine noise, we first of all compared aerodynamic performance such as shaft torque and power with experimentally measured value. Performance results show a good agreement with experimental data within about 0.8%. As the wind speed increases, the overall sound pressure level and the sound pressure level by the quadrupole and dipole source show a increasing tendency. Also, sound pressure level is proportional to $r^{-2}$ in the near field and $r^{-1}$ in the far field according to the increase of distance from the center of hub of wind turbine. According to 2 times increase of distance, sound pressure level is reduced by about 6dB.

• Journal of the Korean Institute of Gas
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• v.20 no.5
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• pp.27-33
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• 2016

The aim of numerical study is the investigation of the solid and fluid temperatures in a reformer tube and chemical reaction characteristics of different steam-carbon ratio. We considered conjugate heat transfer contain radiation, convection and conductive heat transfers. This is because steam reforming reaction of hydrocarbon occurred high temperature conditions up to 800 K- 1000 K by using commercial computational fluid dynamics (CFD) code (Fluent ver. 13.0). For numerical simulation, the Reynolds-Averaged Navier-Stokes, momentum and energy equation were employed. In addition, inside of reformer tube is assumed as the porous medium to consider the Nichrome-based catalyst. To analysis characteristics of tube temperature in chemical reaction, we changed steam-methane ratio(SCR) from 1 to 6. As increased SCR, the higher tube temperature and methane conversion were observed. It was obtained that the highest hydrogen production held in SCR of 5.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.3
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• pp.194-201
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• 2017

The KARI-11-180 airfoil was selected as a model for EFD-CFD comparison workshop case 1. Wind tunnel test for this model was conducted in KARI low speed wind tunnel with $0.6m{\times}3.0m$ model for the Reynolds number up to 3.0E6. The model configuration and wind tunnel test results including Cl, Cd and Cp were released at the KSAS 2015 spring conference. The computational analysis results with KFLOW, FLUENT and STAR-CCM+ were present in the KSAS 2015 fall conference. These computational works were summarized in this paper and the comparison results with each others including the wind tunnel data were also summarized.

• Fire Science and Engineering
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• v.29 no.6
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• pp.33-39
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• 2015

In this paper, a numerical experiment was conducted to find out the optimal location of electrical heat trace for anti-freeze of water inside the CPVC pipe for fire protection. The unsteady incompressible Navier-Stokes equations coupled with energy equation were solved. Since the conduction equation of pipe was coupled with the natural convection of water, the analysis of conjugate heat transfer was conducted. A commercial code (ANSYS-FLUENT) based on SIMPLE-type algorithm was used for investigating the unsteady flows and temperature distributions in water region. From the present numerical experiment, it has been found that the vector field of water inside the PVC pipe is opposite to the case of steel because of the huge difference of material properties of the two pipes. Furthermore, it was found that the lowest part of the pipe was an optimal position for electrical heat trace since the minimum water temperature of the case was higher than those of the other cases.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.54-54
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• 2018

To optimize the deposition parameters of diamond films, the temperature, pressure, and distance between the filament and the susceptor need to be considered. However, it is difficult to precisely measure and predict the filament and susceptor temperature in relation to the applied power in the hot filament chemical vapor deposition (HFCVD) system. In this study the temperature distribution inside the system was numerically calculated for the applied powers of 12, 14, 16 and 18 kW. The applied power needed to achieve the appropriate temperature at a constant pressure and other conditions was deduced, and applied to actual experimental depositions. The numerical simulation was conducted using the commercial computational fluent dynamics software, ANSYS-FLUENT. To account for radiative heat-transfer in the HFCVD reactor, the discrete ordinate (DO) model was used. The temperatures of the filament surface and the susceptor at different power levels were predicted to be 2512 ~ 2802 K, and 1076 ~ 1198 K, respectively. Based on the numerical calculations, experiments were performed. The simulated temperatures for the filament surface were in good agreement with experimental temperatures measured using a 2-color pyrometer. The results showed that the highest deposition rate and the lowest deposition of non-diamond was obtained at a power of 16 kW.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.285-291
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• 2017

In this study, a case analysis for thermal design of electronic equipment using a phase change material(PCM) was performed numerically using ANSYS Fluent. Experiments were conducted to find the temperature increase(${\Delta}T_m$), melting temperature($T_m$), and volume expansion of the PCM under the melting process. To verify the accuracy of the Fluent solver model, $T_m$, ${\Delta}T_m$, and the melting time were compared with experimental results. To simulate the temperature stagnation phenomenon under the melting process, the equivalent specific heat method was applied to calculate the thermal properties of the PCM in the solver model. To determine the thermal stability of electronic equipment, we paid special attention to finding a thermal design for the PCM using fins. Further, an additional numerical analysis is currently underway to find an optimum design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.425-430
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• 2019

Zinc coatings are widely used because of their environmental friendliness and high performance. In general, the coating temperature is a major factor in determining the coating layer thickness and coating quality. In the case of a zinc coating, a uniform and appropriate coating temperature is required. In this study, a thermal flow simulation of the air flow was performed to analyze the temperature distribution of a zinc spray coating room in a natural convection state. Using SolidWorks, modeling was performed for two spray coating rooms, a preheating room, and a drying room, and a thermal flow coupled analysis was performed using ANSYS-FLUENT. As a result of the analysis, the temperature distribution characteristics in the spray coating rooms were determined. It was found that the present temperature was below the target temperature of $25^{\circ}C$. Simulations were conducted for two different boundary conditions (one with a heater added and another with the open part closed). The simulation results show that the method of closing the open part is better than adding the heater.