• 대한안전경영과학회지
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• 제15권2호
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• pp.129-134
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• 2013

In this study, the heat flow analysis compatible commercial code CFX 11 was used to develop the structure inside PCB circuit board devices, which could stable radiant heat as well as the cooling device within it. In case of modifying the arrangement of electronic parts on the PCB inside the multi channel temperature measurement board devices, radiant heat effects did not show a rising tendency, whereas the overall temperature went down in case of installing the vents in the outer case of PCB circuit board devices. In terms of installation location, it was the most appropriate to install it on the electronic parts with no heat. Besides, in case of mounting the fan as a cooling device by considering various user environments for multi channel temperature measurement board devices, the radiant heat effects were shown higher than in case of installing the vents, and the middle sections were the most appropriate to its installation location. In case of changing the wind quantity of the fan from its selected installation location, the best radiant heat effects were shown at high speed as expected.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2007년도 학술논문요약집
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• pp.305-306
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• 2007

ACP(Advanced Spent Fuel Conditioning Process)의 금속전환로에 $U_3O_8$을 공급하기 위하여 20 kgHM/batch의 $UO_2$ 펠릿(pellets)을 처리할 수 있는 건식분말화 장치가 개발되고있다. 건식분말화 장치는 500 $^{\circ}C$온도에서 공기를 공급하여 일정한 입도범위의 균질한 $U_3O_8$을 만든다. 이런 건식 분말화 장치의 효율을 높이기 위해서는 반웅로에 불어 넣어주는 공기의 유량을 증가시킬 필요가 있다. 하지만 공기와 반응하여 생성되는 $U_3O_8$ 입자는 그 크기가 최소 3 ${\mu}$m 정도로 매우 미세하여，반응로 출구를 통해 외부로 빠져나갈 가능성 이있다. 이를 방지하기 위해 분말화 장치 출구 바깥에는 필터가 설치되어 있으나 공기와 함께 $U_3O_8$ 입자가 계속해서 빠져 나갈 경우 입자로 인해 필터가 막혀 제 기능을 할 수 없게 된다. 따라서 건식 분말화 장치는 미세한 $U_3O_8$ 입자가 반응로 밖으로 빠져나가지 않도록 입구에서의 공기 유량을 일정 수준 이하로 조절해주는 것이 필요하다. 이 연구의 목적은 초기 유량으로부터 유량을 점점 증가시키면서 시간변화에 따른 입자 거동 특성을 해석하며， 결과로부터 주어진 크기의 타원입자에 대해 최대 허용 공기 유량을 결정하고자한다. 이 해석을 위해 유동과 입자를 동시에 해석할 수 있는 ANSYS-CFX 5.7.1과 ANSYS-CFX 10.0 두 가지의 소프트웨어가 사용되었다. 해석 결과를 바탕으로 좀더 정확한 유량 한계치 계산을 위해 추가로 수행되어야 할 해석에 대해 제안하였다.

• 한국해안·해양공학회논문집
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• 제27권2호
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• pp.113-117
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• 2015

본 연구에서는 연결재(커플러)로 결합된 라이저의 외부흐름에 따른 3차원 유동-구조 연동해석을 수행하였다. 두 가지 연결재(평면 커플러, 곡면 커플러)를 고려하였으며 ANSYS CFX를 사용하여 수치해석을 수행하였다. 유동해석에서 유동공간은 유입구, 유출구와 대칭 경계조건으로 구성되었으며 연결재의 형상에 따른 항력계수와 유속 분포 결과를 비교하였다. 구조해석에서는 라이저의 응답(최대 변위 및 최대 등가응력)을 통해 연결재의 유용성을 확인하였다.

• 동력기계공학회지
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• 제22권1호
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• pp.25-33
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• 2018

The safety of structure was evaluated by taking into consideration the complex marine environmental conditions of the Lattice boom crane, which is widely used in offshore plants due to less influence by wind. CFX analysis was carried out to take into account the influence of wind speed, and the result was applied as a boundary condition to perform static analysis according to the luffing angles of $28^{\circ}$, $61^{\circ}$, and $80^{\circ}$ in the on board and off board, respectively. In addition, the Lattice Boom Crane is large slender structure, and the possibility of buckling is interpreted under three conditions where the biggest stress occurs. All conditions satisfied the safety requirements of the Classification Regulations. Also, as a result of the buckling analysis, the load less than the critical load was applied so buckling does not occur.

• Nuclear Engineering and Technology
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• 제33권4호
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• pp.397-408
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• 2001

A marine reactor shows very different thermal-hydraulic characteristics compared to a land- based reactor. Especially, study on the variation of flow field due to ship motions such as inclination, heaving and rolling is essential since the flow variation has great influence on the reactor cooling capability. In this study, the natural circulation characteristics of integral type marine reactor with modular steam generators were analyzed using computational fluid dynamics code, CFX-4, for inclined conditions. The numerical analyses are performed using the results of natural circulation experiments for integral reactor which are already conducted at Seoul National University. From the results, it was found that the flow rate in the ascending steam generator cassettes increases due to buoyancy effect. Due to this flow variation, temperature difference occurs at the outlets of the each steam generator cassettes. which is mitigated through downcomer by thermal mixing. Also, around the upper pressure header the flow from descending hot leg goes up to the ascending steam generator cassettes due to large natural circulation driving force in ascending steam generator cassettes. From this result, the increase of How rate in the ascending steam generator cassettes could be understood qualitatively.

• Nuclear Engineering and Technology
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• 제45권2호
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• pp.191-202
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• 2013

A numerical analysis of thermal stratification in the upper plenum of the MONJU fast breeder reactor was performed. Calculations were performed for a 1/6 simplified model of the MONJU reactor using the commercial code, CFX-13. To better resolve the geometrically complex upper core structure of the MONJU reactor, the porous media approach was adopted for the simulation. First, a steady state solution was obtained and the transient solutions were then obtained for the turbine trip test conducted in December 1995. The time dependent inlet conditions for the mass flow rate and temperature were provided by JAEA. Good agreement with the experimental data was observed for steady state solution. The numerical solution of the transient analysis shows the formation of thermal stratification within the upper plenum of the reactor vessel during the turbine trip test. The temporal variations of temperature were predicted accurately by the present method in the initial rapid coastdown period (~300 seconds). However, transient numerical solutions show a faster thermal mixing than that observed in the experiment after the initial coastdown period. A nearly homogenization of the temperature field in the upper plenum is predicted after about 900 seconds, which is a much shorter-term thermal stratification than the experimental data indicates. This discrepancy may be due to the shortcoming of the turbulence models available in the CFX-13 code for a natural convection flow with thermal stratification.

• Nuclear Engineering and Technology
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• 제39권4호
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• pp.327-336
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• 2007

The influence of density differences on the mixing of the primary loop inventory and the Emergency Core Cooling (ECC) water in the downcomer of a Pressurised Water Reactor (PWR) was analyzed at the ROssendorf COolant Mixing (ROCOM) test facility. ROCOM is a 1:5 scaled model of a German PWR, and has been designed for coolant mixing studies. It is equipped with advanced instrumentation, which delivers high-resolution information for temperature or boron concentration fields. This paper presents a ROCOM experiment in which water with higher density was injected into a cold leg of the reactor model. Wire-mesh sensors measuring the tracer concentration were installed in the cold leg and upper and lower part of the downcomer. The experiment was run with 5% of the design flow rate in one loop and 10% density difference between the ECC and loop water especially for the validation of the Computational Fluid Dynamics (CFD) software ANSYS CFX. A mesh with two million control volumes was used for the calculations. The effects of turbulence on the mean flow were modelled with a Reynolds stress turbulence model. The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this circumferential propagation. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. ANSYS CFX was able to predict the observed flow patterns and mixing phenomena quite well.

• 한국추진공학회지
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• 제24권3호
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• pp.71-80
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• 2020

발사체 분석을 위한 CFD 소프트웨어인 LVAFoam을 개발하기 앞서 발사체의 연소기, 터보 펌프 및 외부유동의 시뮬레이션에 사용된 해외의 인하우스 CFD 소프트웨어 및 상용 CFD 소프트웨어에 대한 조사를 수행하였다. 인하우스 소프트웨어로는 NASA, 미시시피 주립대학, DLR, Bertin Technologies & CNES, CERFACS 및 JAXA의 솔버들과, 상용 소프트웨어로는 FLUENT, CFX, Adavance/FrontFlow/red, GASP, CRUNCH CFD, CFD-ACE+, FINE^TM/Turbo, STAR-CCM+ 의 솔버들을 정리하였다. 발사체 분석을 위한 각 소프트웨어의 계산 사례가 제시되었으며, 개발된 LVAFoam이 간략하게 소개되었다.

• 한국기계가공학회지
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• 제21권6호
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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.

• Journal of Korean Dental Science
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• 제16권1호
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• pp.35-46
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• 2023

Purpose: Culture-based methods for microbiological diagnosis and antibiotic susceptibility tests have limitations in the management of orofacial infections. We aimed to profile pus microbiota and identify antibiotic resistance genes (ARGs) using a culture-independent approach. Materials and Methods: Genomic DNA samples extracted from the pus specimens of two patients with orofacial abscesses were subjected to shotgun sequencing on the NovaSeq system. Taxonomic profiling and prediction of ARGs were performed directly from the metagenomic raw reads. Result: Taxonomic profiling revealed obligate anaerobic polymicrobial communities associated with infections of odontogenic origins: the microbial community of Patient 1 consisted of one predominant species (Prevotella oris 74.6%) with 27 minor species, while the sample from Patient 2 contained 3 abundant species (Porphyromonas endodontalis 33.0%; P. oris 31.6%; and Prevotella koreensis 13.4%) with five minor species. A total of 150 and 136 putative ARGs were predicted in the metagenome of each pus sample. The coverage of most predicted ARGs was less than 10%, and only the CfxA2 gene identified in Patient 1 was covered 100%. ARG analysis of the seven assembled genome/metagenome datasets of P. oris revealed that strain C735 carried the CfxA2 gene. Conclusion: A metagenomics-based approach is useful to profile predominantly anaerobic polymicrobial communities but needs further verification for reliable ARG detection.