• Fire Science and Engineering
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• v.33 no.1
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• pp.99-104
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• 2019

In a gas system fire extinguishing system, extinguishing agents are usually stored with approximately 280 bar at $21^{\circ}C$ and are released at approximately 8 MPa through the decompression valve and orifice to quickly suppress the fire. When extinguishing agents are discharged, they cause a loud noise (approximately 140 dB), which can damage electronics, such as hard disk drives (HDDs). Therefore, the noise is becoming a serious issue in the gas extinguishing system. The method of the noise reduction by adding an absorbent is most general and in this study, the thickness of the absorbent was as a selected design variable. The noise level at the observation point and the flow characteristics inside the nozzle were numerically calculated and analyzed using the commercial code ANSYS CFX ver. 18.1.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.28-33
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• 2023

In this study, computational fluid dynamics was used to analyze the flow bias generated as air supplied by a fan passes through ducts, piping, and a coal separation screen. The flow bias of the air flow is mostly caused by the spatial characteristics of the fan volute and duct, and the internal baffle and the coal separation screen at the outlet cause strong pressure losses that dampen the flow bias. ANSYS CFX was used for computational fluid dynamics, and since the baffle and the coal separation screen are shaped like perforated plates with many small holes uniformly distributed, actual modeling for analysis was not possible. Therefore, the Porous Loss Model was applied. The evaluation of the flow bias was analyzed based on the velocity distribution of the Porous Loss Model at the outlet surface of the coal separation screen obtained from the computational fluid dynamics results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.673-680
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• 2017

sump pump is a system that draws in water that is stored in a dam or reservoir. They are used to pump large amounts of water for cooling systems in large power plants, such as thermal and nuclear plants. However, if the flow and sump pump ratio are small, the flow rate increases around the inlet port. This causes a turbulent vortex or swirl flows. The turbulent flow reduces the performance and can cause failure. Various methods have been devised to solve the problem, but a correct solution has not been found for low water level. The most efficient solution is to install an anti-vortex device (AVD) or increase the length of the sump inlet, which makes the flow uniform. This paper presents a computational fluid dynamics (CFD) analysis of the flow characteristics in a sump pump for different sump inlet lengths and AVD types. Modeling was performed in three stages based on the pump intake, sump, and pump. For accurate analysis, the grid was made denser in the intake part, and the grid for the sump pump and AVD were also dense. 1.2-1.5 million grid elements were generated using ANSYS ICEM-CFD 14.5 with a mixture of tetra and prism elements. The analysis was done using the SST turbulence model of ANSYS CFX14.5, a commercial CFD program. The conditions were as follows: H.W.L 6.0 m, L.W.L 3.5, Qmax 4.000 kg/s, Qavg 3.500 kg/s Qmin 2.500 kg/s. The results of analysis by the vertex angle and velocity distribution are as follows. A sump pump with an Ext E-type AVD was accepted at a high water level. However, further studies are needed for a low water level using the Ext E-type AVD as a base.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.938-948
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• 2009

In this paper, permanent magnets were used to remove magnetic sludge in the condenser of the power plant. To obtain the flow characteristics and magnetic information that are needed for determining a proper design of the magnetics sludge removal apparatus, numerical simulations were performed through the use of two commercial codes, ANSYS Workbench-Emag and CFX. Experiments were also performed on various kinds and sizes of magnets to obtain the magnetic information through a gauss meter. By analyzing the results of simulations and experiments, the minimum magnetic force that is able to remove the any size of the magnetic sludge in the condenser was calculated, and the design of the removal apparatus was confirmed. The test model which was confirmed by simulations and experiments was made. After testing, the test results were compared with those of numerical simulations and have good agreements.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.600-605
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• 2009

A general purpose viscous flow solver Ansys CFX is used to study a Savonius type wave energy converter in a 3D numerical viscous wave tank. This paper presents the results of a computational fluid dynamics (CFD) analysis of the effect of blade configuration on the performance of 3 bladed Savonius rotors for wave energy extraction. A piston-type wave generator was incorporated in the computational domain to generate the desired incident waves. A complete OWC system with a 3-bladed Savonius rotor was modeled in a three dimensional numerical wave tank and the hydrodynamic conversion efficiency was estimated. The flow over the rotors is assumed to be two-dimensional (2D), viscous, turbulent and unsteady. The CFX code is used with a solver of the coupled conservation equations of mass, momentum and energy, with an implicit time scheme and with the adoption of the hexahedral mesh and the moving mesh techniques in areas of moving surfaces. Turbulence is modeled with the k.e model. Simulations were carried out simultaneously for the rotor angle and the helical twist. The results indicate that the developed models are suitable to analyze the water flows both in the chamber and in the turbine. For the turbine, the numerical results of torque were compared for all the cases.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.6
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• pp.1-7
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• 2022

This work investigated the performance improvement of a medium-pressure fixed-displacement-type SPUR gear pump, which is mainly used in the machine tool industry. The 3D CFX analysis and IS technique were applied using ANSYS (commercial FEM code) and compared with experimental results to ensure the reliability of the analysis. In addition, the performance improvement of the pump was obtained using the theoretical volumetric displacement equation, and the gear tooth width was changed. The pressure flow performance curves were compared, and the results were analyzed according to the width of the gear teeth. This is a factor that can cause irregular flow, vibration, and noise inside the gear pump owing to friction between the housing and gear pump.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2743-2759
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• 2020

A detailed computational fluid dynamics (CFD) simulation analysis model was developed using ANSYS CFX 16.1 and analyzed to simulate the basic design and internal flow characteristics of a 180 MW small modular reactor (SMR) with a natural circulation flow system. To analyze the natural circulation phenomena without a pump for the initial flow generation inside the reactor, the flow characteristics were evaluated for each output assuming various initial powers relative to the critical condition. The eddy phenomenon and the flow imbalance phenomenon at each output were confirmed, and a flow leveling structure under the core was proposed for an optimization of the internal natural circulation flow. In the steady-state analysis, the temperature distribution and heat transfer speed at each position considering an increase in the output power of the core were calculated, and the conceptual design of the SMR had a sufficient thermal margin (31.4 K). A transient model with the output ranging from 0% to 100% was analyzed, and the obtained values were close to the T_hot and T_cold temperature difference value estimated in the conceptual design of the SMR. The K-factor was calculated from the flow analysis data of the CFX model and applied to an analysis model in RELAP5/MOD3.3, the optimal analysis system code for nuclear power plants. The CFX analysis results and RELAP analysis results were evaluated in terms of the internal flow characteristics per core output. The two codes, which model the same nuclear power plant, have different flow analysis schemes but can be used complementarily. In particular, it will be useful to carry out detailed studies of the timing of the steam generator intervention when an SMR is activated. The thermal and hydraulic characteristics of the models that applied porous media to the core & steam generators and the models that embodied the entire detail shape were compared and analyzed. Although there were differences in the ability to analyze detailed flow characteristics at some low powers, it was confirmed that there was no significant difference in the thermal hydraulic characteristics' analysis of the SMR system's conceptual design.

• The KSFM Journal of Fluid Machinery
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• v.18 no.4
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• pp.43-48
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• 2015

In this study, a method for optimal design of impeller shroud for centrifugal compressor using response surface method (RSM) and multi-objective genetic algorithm (MOGA) was studied. Numerical simulation was conducted using ANSYS CFX with various configurations of shroud. Each of the design parameters was divided into 3 levels. Total 15 design points were planned by central composite design (CCD) method, which is one of the design of experiment (DOE) techniques. Response surfaces based on the results of DOE were used to find the optimal shape of impeller shroud for high aerodynamic performance. The whole process of optimization was conducted using ANSYS Design Xplorer (DX). Results showed that the isentropic efficiency, which is the main performance parameter of the centrifugal compressor, was increased 0.4% through the optimization.

• Journal of computational fluids engineering
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• v.17 no.2
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• pp.11-20
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• 2012

In this paper, the authors test various open codes and commercial codes based on CFD technology on the wind field around the complex terrain, which is a very important transport physics in the event of forrest fire. To study the physical mechanism inside the transition from surface fire to crown fire, the wake flow behind a parallel array of trees is studied numerically to show the flow separation in the turbulent boundary layer. Two sites near to Kunsan National University are chosen for the measurement of real wind field, and obtained data are compared with those from various computational codes such as Wind-Ninja, NIST-FDS, ANSYS-CFX, and ANSYS-FlUENT, etc. Through this research, feasibility and accuracy of the present CFD codes are investigated quantitatively, compared with the measured data with AWS.

• Wind and Structures
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• v.19 no.5
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• pp.523-540
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• 2014

This paper presents a comprehensive study of pressure developed on different faces of a 'Y' plan shape tall building using both numerical and experimental means. The experiment has been conducted in boundary layer wind tunnel located at Indian Institute of Technology Roorkee, India for flow condition corresponding to terrain category II of IS:875 (Part 3) - 1987, at a mean wind velocity of 10 m/s. Numerical study has been carried out under similar condition using computational fluid dynamics (CFD) package of ANSYS, namely ANSYS CFX. Two turbulence models, viz., $k-{\varepsilon}$ and Shear Stress Transport (SST) have been used. Good conformity among the numerical and experimental results have been observed with SST model yielding results of higher magnitude. Peculiar pressure distribution on certain faces has been observed due to interference effect. Furthermore, flow pattern around the model has also been studied to explain the phenomenon occurring around the model.