• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.516-520
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• 2009

This study describes aerodynamic characteristics for the HAWT (Horizontal Axis Wind Turbine) rotor blade using general CFD(Computational Fluid Dynamics) code. The boundary conditions for analysis are validated with the experimental result by the NREL (National Renewable Energy Laboratory)/NASA Ames wind tunnel test for S809 airfoil. In the case of wind turbine rotor blade, complex phenomena are appeared such as flow separation and re-attachment. Those are handled by using a commercial flow analysis tool. The 2-equation k-$\omega$ SST turbulence model and transition model appear to be well suited for the prediction. The 3-dimensional phenomena in the HAWT rotor blade is simulated by a commercial 3-D aerodynamic analysis tool. Tip vortex geometry and Radial direction flows along the blade are checked by the analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.177-180
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• 2007

A three dimensional numerical analysis has been made for the cone disk control valve and the flat disk control valve. The simulation of the incompressible flow in the each control vale are performed by using the commercial code. Six flow cases of each control valve are investigated.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.448-451
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• 2008

Three methods of nozzle flow analysis, frozen-equilibrium, shifting-equilibrium and non-equilibrium approaches, were used to rocket nozzle flow, those were coupled with the methods of computational fluid dynamics code. For a design of high temperature rocket nozzle, chemical equilibrium analysis which shares the same numerical characteristics with frozen flow analysis can be an efficient design tool for predicting maximum thermodynamic performance of the nozzle. Frozen fluid analysis presents the minimum performance of the nozzle because of no consideration for the energy recovery. On the other hand, the case of chemical-equilibrium analysis is able to forecast the maximum performance of the nozzle due to consideration for the energy recovery that is produced for the fast reaction velocity compared with velocity of moving fluid. In this study, using the chemical equilibrium flow analysis code that is combined the modified frozen-equilibrium and the chemical-equilibrium. In order to understand the thermochemical characteristic components and the accompanying energy recovery, shifting-equilibrium flow analysis was carried out for the 30 $ton_f$-class KARI liquid rocket engine nozzle together with frozen flow. The performance evaluation based on the 30 $ton_f$-class KARI LRE nozzle flow analyses will provide an understanding of the thermochemical process in the nozzle and performances of nozzle.

• Nuclear Engineering and Technology
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• 제52권4호
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• pp.755-763
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• 2020

The critical flow phenomenon has been studied because of its significant effect for design basis accidents in nuclear power plants. Transition points from thermal non-equilibrium to equilibrium are different according to the geometric effect on the critical flow. This study evaluates the uncertainty parameters of the critical flow model for analysis of DBA (Design Basis Accident) with the MARS-KS (Multi-dimensional Analysis for Reactor Safety-KINS Standard) code used as an independent regulatory assessment. The uncertainty of the critical flow model is represented by three parameters including the thermal non-equilibrium factor, discharge coefficient, and length to diameter (L/D) ratio, and their ranges are determined using large-scale Marviken test data. The uncertainty range of the thermal non-equilibrium factor is updated by the MCDA (Model Calibration through Data Assimilation) method. The updated uncertainty range is confirmed using an LBLOCA (Large Break Loss of Coolant Accident) experiment in the LOFT (Loss of Fluid Test) facility. The uncertainty ranges are also used to calculate an LBLOCA of the APR (Advanced Power Reactor) 1400 NPP (Nuclear Power Plants), focusing on the effect of the PCT (Peak Cladding Temperature). The results reveal that break flow is strongly dependent on the degree of the thermal non-equilibrium state in a ruptured pipe with a small L/D ratio. Moreover, this study provides the method to handle the thermal non-equilibrium factor, discharge coefficient, and length to diameter (L/D) ratio in the system code.

• 소음진동
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• 제9권1호
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• pp.85-96
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• 1999

For ASME Code pumps in nuclear power plants, inservice test is required to assess the operational readiness in accordance with ASME code and related regulations. The objective of this study therefore, is to develop the technical background of the degradation of pump performances and conditions due to low flow rate operation. In addition. the detection techniques of pump operating conditions are to be developed to enhance the safety and economy of nuclear power plants. A test loop consisted of pump, motor. water tank, flow rate measurements and piping system with flow control devices was established for this study. Two typical pumps, 1-stage volute pump and 3-stage turbine pump, were selected and the test was performed upon two major point of views ; i.e., pump discharge pressure pulsations analysis and pump vibration spectrum analysis. From the test results, it is concluded that (1) the pump vibration affected by the natural frequency of operating pump is significant in the low frequency zone (around 1 Hz) : the vibration amplitude. especially. is an important factor during low flow rate operation. and shall be monitored to ensure that it is within the limit of ASME OM code Part 6, (2) the vibration frequency and pump discharge pressure are affected by vane pass frequency and running speed, (3) the wave phenomena due to the compressiblity of water is anticipated during low flow rate operation. and the pump system shall be designed to prevent it and. finally, (4) the technical background of the degradation of pump performances and conditions due to low flow rate operation is provided.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.696-701
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• 2001

The performance and the internal flow of the impeller of the centrifugal chiller compressor with refrigerant R12 as working fluid were studied numerically, using CFD code, CFX-Tascflow, which is commercially available. In this numerical study, the thermodynamic and transport properties of the refrigerant gas were generated by the property program of NIST and linked with main program to extend the capability of the code to refrigerant gases. Numerical study was applied to several mass flow rates near the design mass flow rate at constant rotating speed. Overall performance and flow characteristics of the impeller at impeller exit were investigated. The results were physically reasonable and showed good agreement with experimental measurement at the design flow rate.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3775-3786
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• 2023

Mixing Vane Grid (MVG) is one of the most important structures in fuel assembly due to its high performance in mixing the coolant and ultimately increasing Critical Heat Flux (CHF), which avoids the temperature rising suddenly of fuel rods. To evaluate the mixing performance of the MVG, a Total Diffusion Coefficient (TDC) mixing coefficient is defined in the subchannel analysis code. Conventionally, the TDC of the spacer grid is obtained from the combination of experiments and subchannel analysis. However, the processing of obtaining and determine a reasonable TDC is much challenging, it is affected by boundary conditions and MVG geometries. In is difficult to perform all the large and costing rod bundle tests. In this paper, the CFD method was applied in TDC analysis. A typical 5 × 5 MVG was simulated and validated to estimate the mixing performance of the MVG. The subchannel code was used to calculate the TDC. Firstly, the CFD method was validated from the aspect of pressure drop and lateral temperature distribution in the subchannels. Then the effect of boundary conditions including the inlet temperature, inlet velocities, heat flux ratio between hot and cold rods and the arrangement of hot and cold rods on MVG mixing and TDC were studied. The geometric effects on mixing are also carried out in this paper. The effect of vane pattern on mixing was investigated to determine which one is the best to represent the grid's mixing performance.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 추계 학술대회논문집
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• pp.31-36
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• 2001

The velocity and temperature profiles in the cabin of the automobile affect greatly to the comfort of the passenger. In this paper, the three dimensional flow and temperature analysis in the cabin of the automobile which is geometrically complicated was performed to investigate and predict the velocity and temperature profile. The three dimensional Navier-Stokes code used in this case was validated by performing of a 1/5 experimental scale model vehicle flow anal)rsis successfully. The temperature field of cavity was analyzed for Energy-equation code validation. The comparison of the results are made with the polished computational data and give a coincided one.

• 대한조선학회논문집
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• 제44권4호
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• pp.370-378
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• 2007

In this study. a numerical analysis has been performed for the turbulent flow around a 15,000TEU twin-skeg container ship using a commercial CFD code. FLUENT. The computed results have been compared with the model test data from MOERI. We investigated viscous resistance coefficient. wake distribution and characteristics of the shear flow according to the grid numbers. Although the free surface is approximated by the plane of symmetry in this work. the calculated axial velocity and transverse vector show a good agreement with the MOERI experimental data except for the region of 0.9 level of axial velocity at the propeller plane. The numerical analysis show that commercial CFD code is useful tool for the evaluation of complex hull form with twin-skegs.

• 한국전산유체공학회지
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• 제21권2호
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• pp.47-53
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• 2016

This study investigated natural convection flow behavior in airflow path designed in concrete dry storage cask to remove the decay heat from spent nuclear fuels. Using FLUENT 16.1 code, thermal analysis for natural convection was carried out for three dimensional, 1/4 symmetry model under the normal condition that inlet ducts are 100% open. The maximum temperatures on other components except the fuel regions were satisfied with allowable values suggested in nuclear regulation-1536. From velocity and temperature distributions along the flow direction, the flow behavior in horizontal duct of air inlet and outlet duct, annular flow-path and bent pipe was delineated in detail. Theses results will be used as the theoretical background for the composing of airflow path for the designing of passive heat removal system by understanding the flow phenomena in airflow path.