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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of computational fluids engineering
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Journal DOI :
Korea Society of Computational Fluids Engineering
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Volume & Issues
Volume 15, Issue 4 - Dec 2010
Volume 15, Issue 3 - Sep 2010
Volume 15, Issue 2 - Jun 2010
Volume 15, Issue 1 - Mar 2010
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EVALUATION OF METHODOLOGY FOR AXISYMMETRIC SIMULATION OF RCCS IN VHTR
Kim, S.H. ; Cho, B.H. ; Tak, N.I. ; Kim, M.H. ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 1~8
RCCS is a passive safety-related system that removes the decay heat of VHTR when normal decay heat removal systems are in failure. Understanding thermo-hydraulics of RCCS is important to design a safer VHTR. RCCS consists of 292 cooling panels, which are placed in the reactor cavity. The layout of RCCS gives an idea that, for CFD simulations, cooling panels can be assumed to be one annulus tube. This assumption can reduce significantly the computational time, especially for the unsteady simulation. To simulate RCCS in an axisymmetric manner, three models were suggested and compared. Each model has (1) the same outer radius, (2) the same cross-sectional area (3) the same pressure drop, respectively, as the RCCS cooling panels. The steady-state simulation was conducted with these three models and the DO radiation model. It is found that over 90% of the heat from the outer wall of the reactor pressure vessel is transported to the RCCS by radiative heat transfer. The simulation with the third model, which has the same pressure drop as the design, estimates the closest wall temperature profiles to a thermo-hydraulic code, GAMMA+, result.
HEAT TRANSFER CHARACTERISTICS IN A FAST PYROLYSIS REACTOR FOR BIOMASS
Choi, Hang-Seok ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 9~16
The characteristics of flow and heat transfer in a bubbling fluidized bed are investigated by means of computational fluid dynamics (CFD). To simulate two-phase flow for the gas and solid flows, Eulerian-Eulerian approach is applied. Attention is paid for a heat transfer from the wall to fluidized bed by bubbling motion of the flow. From the result, it is confirmed that heat transfer is promoted by chaotic bubbling motion of the flow by enhancement of mixing among solid particles. In particular, the vortical flow motion around gas bubble plays an important role for the mixing and consequent heat transfer. Discussion is made for the time and space averaged Nusselt number which shows peculiar characteristics corresponding to different flow regimes.
NUMERICAL STUDY ON FLOW CHARACTERISTIC IN THE HEAT RECOVERY STEAM GENERATOR
Choi, H.K. ; Yoo, G.J. ; Shin, B.J. ; Kim, C.H. ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 17~23
Performance improvements of the heat recovery steam generator(HRSG) can be achieved by improving the flow distribution of exhaust gases for a various type of different equipments. A number of design parameters are systematically investigated and their effects on an index of velocity deviation established. The parameters include the three shape of the transition duct and the wide range of the guide vane angles. The numerical results clearly reveal feature of the flow pattern in the transition duct, velocity deviation and pressure drop at tube bank part.
PRELIMINARY ON-ORBIT THERMAL ANALYSIS FOR THE GEOSTATIONARY OCEAN COLOR IMAGER OF COMS
Kim, Jung-Hoon ; Jun, Hyoung-Yoll ; Han, Cho-Young ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 24~30
A preliminary thermal analysis is performed for the optical payload system of a geostationary satellite. The optical payload considered in this paper is GOCI(Geostationary Ocean Color Imager) of COMS of Korea. The radiative and conductive thermal models are employed in order to predict thermal responses of the GOCI on the geostationary orbit. The results of this analysis are as follows: 1) the GOCI instrument thermal control is satisfactory to provide the temperatures for the GOCI performances, 2) the thermal control is defined and interfaces are validated, and 3) the entrance baffle temperature and shutter wheel motor gradient are found slightly out their specification, therefore further detailed analyses should be continued on these elements.
COMPUTATIONAL STUDY FOR PERFORMANCE EVALUATION OF FLOW CHANNELS INSIDE CDI UNIT CELL
Sohn, D.Y. ; Choi, Y.H. ; Park, D.W. ; Jung, C.H. ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 31~36
In the present study, computations for flow fields inside the CDI unit cells with electrodes and spacers have been made to evaluate their performance. Three types of unit cells that include a planar type, a serpentine channel type, and a spiral wound type were considered and their flow characteristics were compared. From the computational results, it is found that the serpentine channel type has a large flow resistance and can not guarantee the outflow flux for industrial applications. On the other hand, the planar type can sustain a large enough outflow flux but it's efficiency is low for the electrode-use because of the non-uniform velocity distribution inside the cell and dead zones in every corner. Finally, The spiral wound type has not only a large outflow flux as much as the planar type has, but also a high efficiency for the electrode-use because of uniform velocity distribution. From this comparison, we can expect that the spiral wound type of CDI unit cell would have a high performance deionization capability.
THE COMPUTATION OF UNSTEADY FLOWS AROUND THREE DIMENSIONAL WINGS ON DYNAMICALLY DEFORMING MESH
Yoo, Il-Yong ; Lee, Byung-Kwon ; Lee, Seung-Soo ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 37~45
Deforming mesh should be used when bodies are deforming or moving relative to each other due to the presence of aerodynamic forces and moments. Also, the flow solver for such a flow problem should satisfy the geometric conservation law to ensure the accuracy of the solutions. In this paper, a RANS(Reynolds Averaged Navier-Stokes) solver including automatic mesh capability using TFI(Transfinite Interpolation) method and GCL is developed and applied to flows induced by oscillating wings with given frequencies. The computations are performed both on deforming meshes and on rigid meshes. The computational results are compared with experimental data, which shows a good agreement.
INFLUENCE OF THE THERMAL CONTACT RESISTANCE ON THE FIN-TUBE HEAT EXCHANGER PERFORMANCE
Yoo, S.S. ; Lee, M.S. ; Han, B.Y. ; Park, H.K. ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 46~55
In this study, the heat transfer and fluid flow characteristics of a condenser for a refrigerator are analyzed with the numerical method. The main objective of the study is to obtain basic data in order to develop a new type of condenser focused on an influence of thermal resistance of air side and thermal contact resistance on the heat transfer performance. The CFD technique was used for whole study, and experiments were performed in order to verify the reliability of the numerical analysis and predict the thermal contact resistance. In this study, a heat exchanger sample was made of a part of condenser to make the experimental and numerical analysis simple and efficient. Water was used for the inner working fluid of the heat exchanger, and an experimental apparatus was composed concisely. A heat exchanger sample of tube type was used to verify the reliability of numerical analysis, and a heat exchanger of fin and tube type was used to predict the ratio of thermal contact resistance to the overall thermal resistance.
A STUDY ON FLOW MIXING IMPROVEMENT OF SELECTIVE CATALYTIC REDUCTION USING GASEOUS REDUCTANT
Ko, S.C. ; Lee, B.H. ; Cho, S.H. ; Lee, S.H. ; Hong, S.T. ; Lee, D.Y. ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 56~63
Since emission regulations for vehicles have become more stringent, SCR technology has drawn a strong attention in order to reduce NOx emissions. Optimal design of a reductant injection nozzle and a multi-hole plate located between the cone and catalyst is critical in that the uniform distribution of reductant is necessary to maximize the NOx conversion efficiency and minimize the slip of reductant in SCR. In this work, an LPG fuel(C3H8 in vapor state) was used as a reductant for LPG vehicles. A Realizable k-
model is used for turbulence, and SCR body is defined as porous media with inertia and viscous resistances measured in this work. Effect of the number of nozzle holes on the flow mixing index was analyzed, which revealed that a four hole nozzle shows the best performance in terms of uniformity of flow. An installment of a multi-hole plate at the entrance of catalyst was evaluated with flow mixing index, uniformity of flow, and pressure drop. A multi-hole plate with gradual hole diameter change in three steps showed the best uniformity of flow within the conditions suggested in this work.
CHARACTERISTIC OF BUTTERFLY VALVE FLOW WITH DIFFERENT DESIGN FACTORS
Lee, J.W. ; Choi, H.K. ; Yoo, G.J. ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 64~70
Flow control butterfly valve(FCBV) is known to have difficulty in controlling flow rate along valve opening due to its high flow rate. In low opening condition, the butterfly valve also has some shortcomings such as noise, vibration and erosion which are mostly caused by cavitation effects. Therefore, the FCBV requires proper remedies to reduce cavitation effects and to improve flow control performance. Numerical analysis is applied to FCBV flow to find effects of design factors such as seat diameter and valve opening rate. Cases with 3 different sizes of seat diameter and various valve opening rate are selected for the numerical analysis. From the analysis results, it is found that the FCBV with small seat diameter shows better pressure loss performance and reduced cavitation effects.
IMPROVEMENT OF MPS METHOD IN SIMULATING VIOLENT FREE-SURFACE MOTION AND PREDICTING IMPACT-LOADS
Hwang, S.C. ; Lee, B.H. ; Park, J.C. ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 71~80
The violent free-surface motions and the corresponding impact loads are numerically simulated by using the Moving Particle Semi-implicit (MPS) method, which was originally proposed by Koshizuka and Oka (1996) for incompressible flows. In the original MPS method, there were several shortcoming including non-optimal source term, gradient and collision models, and search of free-surface particles, which led to less-accurate fluid motions and non-physical pressure fluctuations. In the present study, how those defects can be remedied is illustrated by step-by-step improvements in respective processes of the revised MPS method. The improvement of each step is explained and numerically demonstrated. The numerical results are also compared with the experimental results of Martin and Moyce (1952) for dam-breaking problem. The current numerical results for violent free-surface motions and impact pressures are in good agreement with their experimental data.
SHIP RESISTANCE AND PROPULSION PERFORMANCE TEST USING HYBRID MESH AND SLIDING MESH
Lee, Ju-Hyun ; Park, Bum-Jin ; Rhee, Shin-Hyung ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 81~87
In this study, we conducted resistance and propulsion performance test of ship composed of the Resistance Test, Propeller Open Water Test and Self Propulsion Test using the CFD(Computational Fluid Dynamics). We used commercial RANS(Reynolds Averaged Navier Stokes equation) solver, as a calculating tool. The unstructured grids were used in a bow and stern of ship, having complex shape, for a convenience of generating grids, and the structured grids were adopted in a central hull and rest of hull having a relatively simple shape which is called hybrid grid method. In addition, The sliding mesh method was adopted to rotate a propeller directly in the Propeller Open Water and Self Propulsion Test. The Resistance Test and Self Propulsion Test were calculated using Volume of Fluid (VOF) model and considering a free surface. And all The three cases were applied realizable k-epsilon model as the turbulence model. The results of calculations were verified for the suitability of calculations by comparing MOERI's EFD results.
DEVELOPMENT OF WEB-BASED JAVA PROGRAM FOR NUMERICAL ANALYSIS OF PIPE FLOW
Kim, K.S. ; Park, J.C. ;
Journal of computational fluids engineering, volume 15, issue 1, 2010, Pages 88~94
In general, flow analysis programs have been built in not JAVA language but such as Fortran, C or C++ because of a merit in performance of computation. However, most developer of those languages are not free for use. User should purchase the development tools of programs, and install it on their own computer. Fortunately, JAVA is a free software, and can be used to develop WEB-based programs. It is well known that the JAVA language is time consuming for calculating. However, the performance of computer power has been increased continuously, so it is sure that the former states can be overcome. In the present study, a flow analysis program, which is interactive with Graphics, using the Web-based programing language, JAVA, has been developed for solving the two-dimensional flow motion.