• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.526-529
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• 2008

Air Conditioner has become a popular comfort providing device since two decades, whether in an office or home especially for warm and wet climate countries. The RAC (Room Air Conditioner) is widely used in various working spaces and residences. It composed of heat exchager, cross-flow fan, stabilizer, rearguider and blade of diffuser region, etc. In this study, numerical analyses based on the prediction of transient phenomena were carried out to investigate the flow characteristics in the RAC, including the impeller, the rearguider, the stabilizer and the blade of the diffuser region. Using a commercial code, FLUENT, the velocity, pressure and streamlines were obtained with unsteady, turbulent flow and no-slip condition. The angular velocities of impeller are located in the 900 rpm. Turbulent closure was achieved using a standard k-${\varepsilon}$ model. A moving reference frame (MRF) approach was adopted to simulate the flow field generated by impeller in the RAC. Results were graphically depicted with various geometrical configurations and operating conditions.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.174-180
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• 1998

Numerical study of three-dimensional turbulent flow in a forward curved centrifugal fan is presented. Standard $k-{\varepsilon}$ turbulence model and non-orthogonal curvilinear coordinates are used to consider the turbulent flow field and complex geometry. Finite Volume approach is adopted for discretization scheme and structured grid system is used to help convergence. Multiblock grid system is used for flow field and divided into five domains that are inlet, outlet, impeller, tip clearance and scroll. It is assumed that the flow field is steady state and incompressible. This numerical work is performed with commercial CFD-ACE code developed by CFD Research Corporation, and the results are compared wi th the experimental data

• 한국전산유체공학회:학술대회논문집
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• 1997.10a
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• pp.29-37
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• 1997

An implicit viscous turbulent flow solver is developed for two-dimensional geometries on unstructured triangular meshes. The flux terms are discretized based on a cell-centered finite-volume formulation with the Roe's flux-difference splitting. The solution is advanced in time using an implicit backward-Euler time-stepping scheme. At each time step, the linear system of equations is approximately solved with the Gauss-Seidel relaxation scheme. The effect of turbulence effects is approximated with a standard $k-{\varepsilon}$ two-equation model which is solved separately from the mean flow equations using the same backward-Euler time integration scheme. The triangular meshes are generated using an advancing-front/layer technique. Validations are made for flows over the NACA0012 airfoil and the Douglas 3-element airfoil. Good agreements are obtained between the numerical results and the experiment.

• Fire Science and Engineering
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• v.19 no.1 s.57
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• pp.87-92
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• 2005

In this paper, numerical simulation are conducted to predict the characteristics of the heat transfer and smoke flow and evacuation in the road tunnel. Fire source are used about 30 MW and the turbulent flow characteristics are considered by standard k-epsilon turbulent model. The effect of transient thermal behavior and disaster prevention can be used for designing the road tunnel.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.552-558
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• 1999

Ventilation of the marine engine room is very important for the health of the workers as well as the normal operation of machines. To find proper ventilation conditions of this engine room numerical simulation with a standard k-$\varepsilon$model was carried out. In the present study the marine engine room is considered as a closed space with a heat source and forced ventilation ducts. The injection angle of air supply is found to be important. Injection with a downward angle depresses recirculation flow causing a strong stream in the wider space of the room Ventilation and removal of the released heat are promoted with this pattern, There is a possibility of local extreme heating at the upper surface of the engine when supply and exhaust ports of air are in bilateral symmetry.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.10
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• pp.908-916
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• 2000

In this paper, the characteristics of moisture ventilation in the lithium ion battery manufacturing dry room are studied numerically using standard $k-\varepsilon$ turbulence model. Both the steady-state and the unsteady behaviors of moisture ventilation are analyzed by considering local and uniform moisture generation. In order to evaluate the characteristics of moisture ventilation, three scales of ventilation efficiency and characteristic ventilation time are presented from the numerical results. It was shown that moisture distribution was dependent strongly on the flow field. The characteristics of moisture ventilation were improved by 20% and 40% in terms of the 1st scale of ventilation efficiency (SVE1) and the 2nd scale of ventilation efficiency (SVE2), respectively, through the modifications of design variables such as the addition of inlets, outlets and partition. A significant improvement in the characteristic ventilation time and the moisture exhaust efficiency was also made by these modifications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.916-923
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• 2000

Numerical study of three-dimensional turbulent flow in a forward curved centrifugal fan is presented. Standard $k-{\varepsilon}$ turbulence model and non-orthogonal curvilinear coordinates arc used to consider the turbulent flow field and complex geometry. Finite Volume approach is adopted for discretization scheme and structured grid system is used to help convergence. Multiblock grid system is used for flow field and divided into five domains that are inlet, outlet, impeller, tip clearance and scroll. It is assumed that the flow field is steady and incompressible. These numerical results are compared with the experimental data inside a rotor and at the fan outlet. Most important flow features are captured through this numerical approach. Finally details of flow field inside a fan are described and analyzed.

• Journal of Industrial Technology
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• v.18
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• pp.335-341
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• 1998

A numerical investigation was performed to determine the effect of a Gurney flap on a NACA 23012 airfoil. A Navier-Stokes code, RAMPANT, was used to calculate the flow field about airfoil. The fully turbulent results were obtained using the standard $k-{\varepsilon}$ two-equation turbulence model. To provide a check case for our computational method, computations were performed for NACA 4412 airfoil which compared with Wedcock's experimental data. Gurney flap sizes of 0.5, 1.0, 1.5, and 2% of the airfoil chord were studied. The numerical solutions showed the Gurney flap increased both lift and drag. These results suggested that the Gurney flap served to increased the effective camber of the airfoil. But Gurney flap provided a significant increase in lift-to-drag ratio relatively at low angle of attack and for high lift coefficient. Also, it turned out that 0.5% chord size of flap was best one among them.

• Journal of ILASS-Korea
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• v.24 no.3
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• pp.122-129
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• 2019

Flow uniformity in aftertreatment system is an important factor in determining uniform catalytic reaction and filtration. In this study, variety types of DOC-DPF system design were analyzed to increase flow uniformity. For this analysis, ANSYS Fluent was used with porous media setup for DOC and DPF. Turbulent flow was modeled by standard $k-{\varepsilon}$ model excepting porous media. Uniformity index was utilized to evaluate the flow uniformity quantitatively. Reference design showed low velocity region because two large vortex were generated before baffle. When radius of DOC-DPF system was increased, exhaust pressure acting on the inlet decreases and velocity distribution was shifted to one side. When inlet pipe was set to axial center of DOC-DPF system velocity distribution was symmetric. However, flow was not dissipated until the front end of DOC and showed higher uniformity index. When the volume of DOC was reduced while fixed volume of entire DOC-DPF system and baffle plate is located downstream of the DOC-DPF system, there was improvement in uniformity index.

• Transactions of the KSME C: Technology and Education
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• v.3 no.3
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• pp.233-240
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• 2015

Analysis of the aerodynamic performance of a bobsleigh has been performed for various types of bobsleigh body shape. To analyze the aerodynamic performance of the bobsleigh, three-dimensional Reynolds-averaged Navier-Stoke equations were used with the standard k-${\varepsilon}$ model as a turbulence closure. Grid structure was composed of unstructured tetrahedral grids. The radii of curvature of cowling, and height and length of front bumper at the tip on the drag coefficient were selected as geometric parameters. And, the effects of these parameters on the aerodynamic performance, i.e., the drag coefficient, were evaluated. The results shows that the aerodynamic performance is significantly affected by the height of front bumper and radius of curvature.