수평 상향 분사 덕트를 이용한 컨테이너선 화물창 환기 개선에 대한 실험적 연구

박일석(Il Seouk Park),박상민(Sang Min Park),하지수(Ji Soo Ha) 대한조선학회 2006 大韓造船學會 論文集 Vol.43 No.2

열간압연 이후 주행하는 고온 강재의 냉각해석에서 소재의 물성변화 효과 연구

박일석(Il Seouk Park),박정은(Jung Eun Park) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.5

열연 판재 제조과정에서는 제품의 강도와 인성을 제어하기 위해 압연 직후 800℃ 이상의 고온 소재를 수냉각 방식으로 급속 냉각시킨다. 이 과정에는 소재 표면과 냉각수 사이의 비등 열전달 현상과 소재 표면에 쌓이는 체류수의 자유표면 유동, 소재의 고속 주행 등 매우 복잡한 물리현상들을 포함하고 있다. 본 연구에서는 이 모든 물리 현상들을 수치적으로 모델링한 해석 모델을 적용하여 기본 열전달 해석을 수행한다. 실제로 소재는 냉각에 의해 내부에서 오스테나이트로부터 페라이트로 상변태가 일어나고 이로 인해 소재의 국부적인 열물성치의 변화가 발생하지만 본 연구에서는 상변태를 직접 푸는 방법 대신 이미 알려진 소재의 온도에 따른 물성변화 곡선을 이용하여 냉각해석을 수행하고 이를 기존의 일정 물성치 조건에서 해석한 결과와 비교하여 소재의 물성변화가 소재 냉각에 미치는 영향과 상변태 해석의 필요성에 대해 검토하였다. In the manufacturing process of steel plates, materials at high temperatures above 800°C are rapidly cooled by using a circular impinging water jet to determine their strength and toughness. In this study, the basic heat and fluid flow is solved by using the existing numerical model for boiling heat transfer. Actually, steel undergoes a phase change from austenite to ferrite or bainite during the cooling process. The phase change induces changes in its thermal properties. Instead of directly solving the phase change and the material cooling together, we solve the heat transfer only by applying the thermal properties that vary with temperature, which is already known from other studies. The effects of the changes in the thermal properties on the cooling of steel and the necessity of calculating the phase change are discussed.

수직평판을 타고 흐르는 층류파동액막류에 대한 체적분율식 시간차분법에 따른 해석 결과 비교

박일석(Il Seouk Park),김영조(Young Jo Kim),민준기(June Kee Min) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.11

액막류는 레이놀즈수 및 유동 안정성에 의해 파동이 없는 층류액막류, 파동을 동반한 층류 액막류 및 난류액막류로 구분된다. 파동액막류는 강한 비선형성에 의해 매우 복잡하여 기존에는 주로 실험적 연구가 진행되었다. 수치적 해석은 주로 파동이 없는 경우에 국한되었으며 여러 가지 자유표면 해석기법을 이용하여 평균액막두께를 예측하였다. 이 연구에서는 층류액막류의 파동현상을 레이놀즈수 20~1000 범위에서 수치해석하였다. 이 때, VOF 자유표면 해석기법에 기반한 여러 가지 수치방법을 비교 연구하였으며 평균액막두께, 파동속도 및 진폭을 실험결과와 비교하였다. Liquid film flows are classified into waveless laminar, wavy laminar, and turbulent flows depending on the Reynolds number or the flow stability. Since the wavy motions of the film flows are so intricate and nonlinear, studies on them have largely been experimental. Most numerical approaches have been limited to the waveless flow regime. The various free surface?tracking schemes adopted for this problem were used to more accurately estimate the average film thickness, rather than to capture the unsteady wavy motion. In this study, the wavy motions in laminar wavy liquid film flows with Reynolds numbers of 200?1000 were simulated with various numerical schemes based on the volume of fluid (VOF) method for interface tracking. The results from each numerical scheme were compared with the experimental results in terms of the average film thickness, the wave velocity, and the wave amplitude.

흡진 수직 증발관에서 유동 및 열/물질 전달 해석

박일석(Il-Seouk Park),최도형(Do Hyung Choi) 한국전산유체공학회 1998 한국전산유체공학회 학술대회논문집 Vol.1998 No.-

A numerical investigation for the flow, heat and mass transfer characteristics of the grooved evaporating tube with the films flowing down on both the inside and outside tube walls has been carried out. The condensation occurs along the outside wall while the evaporation takes place at the free surface of the inside film. The 3-D transport equations for momentum and energy are solved by using the FVM(Finite Volume Method), The free surface shape is tracked by the moving grid technique satisfying the SCL(Space Conservation Rule). Due to the secondary motion of the fluid, the film thins at the crest, while thickens at the valley. The velocity and temperature fields as well as the amounts of the 'condensed and evaporated mass have been successfully predicted for various operating conditions and groove shapes.

공기기둥이 형성된 원통 용기의 내부유동 특성에 관한 수치해석 연구

박일석(Il Seouk Park),손종현(Jong Hyeon Son),손창현(Chang Hyun Sohn) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.3

액체가 차있는 원통 용기를 회전 시킨 후 바닥 중앙에 위치한 원형 배수구로 액체를 배수시키면 공기 기둥이 형성된다. 공기기둥이 발생하면, 배수 유량이 감소하고 배수 시간도 지연된다. 본 연구에서는 공기기둥 형성과 배수과정 중의 용기내부의 유동특성을 수치해석 방법으로 관찰하였다. 다양한 격자계와 시간차분방법을 적용하였고 적합한 방식을 얻기 위해 실험결과와 비교하였다. 여러 위치에서의 축방향, 반경방향, 원주방향 속도 성분들의 분포를 시간대 별로 나타내었고, 속도 벡터와 유선 분포 도시를 통하여 내부 유동 구조를 분석하였다. An air core is generated during draining through an axisymmetrically placed circular orifice after rotating a cylindrical tank filled with a liquid. If an air core is generated, the draining flow rate decreases and the draining time increases. In this study, the process of the formation of the air core and internal flow characteristics in a cylindrical tank are studied by numerical methods. Several methods are used in the analysis, and the results are compared with experimental results to obtain the appropriate scheme. Axial, radial, and swirl velocity profiles on a variety of heights are shown graphically, and the internal flow structure is analyzed from the velocity profiles, the vector plot, and the stream function distribution.

전산해석을 통한 고압열증기압축기 형상변수에 관한 강건 설계

박일석(Park Il Seouk) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.12

A high motive pressure thermal vapor compressor(TVC) for a commercial multi-effect desalination(MED) plant is designed to have a high entraining performance and its robustness is also considered in the respect of operating stability at the abrupt change of the operating pressures like the motive and suction steam pressure which can be easily fluctuated by the external disturbance. The TVC having a good entraining performance of more than entrainment ratio 6.0 is designed through the iterative CFD analysis for the various primary nozzle diameter, mixing tube diameter and mixing tube length. And then for a couple of TVC having a similar entrainment ratio, the changes of the entrainment ratio are checked along the motive and suction pressure change. The system stability is diagnosed through the analyzing the changing pattern of the entrainment ratio.

다양한 대기풍속 및 대기온도 구배 조건에서의 공장 배출 가스의 확산 특성에 관한 연구

박일석(Il Seouk Park) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.11

The dispersion of plume which is emitted from a chimney is governed by a lot of factors:wind, local terrain, turbulence intensity of atmosphere, and temperature, etc. In this study, we numerically investigate the plume dispersions for various altitudinal temperature gradients and wind speeds. The normal atmosphere has the temperature decrease of 0.6℃/100 m, however, actually the real atmosphere has the various altitudinal temperature profiles according to the meteorological factors. A previous study focused on this atmospheric temperature gradient which induces a large scale vertical flow motion in the atmosphere thus makes a peculiar plume dispersion characteristics. In this paper, the effects of the atmospheric temperature gradient as well as the wind speed are investigated concurrently. The results for the developing processes in the atmosphere and the affluent’s concentrations at the ambient and ground level are compared under the various altitudinal temperature gradients and wind speeds.

내부와 외부에서 증발과 응축이 발생하는 수직관에 대한 유동 해석

박일석(Il Seouk Park) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.8

A numerical study for the flow, heat and mass transfer characteristics of the evaporating tube with the films flowing down on both the inside and outside tube walls has been carried out. The condensation occurs along the outside wall while the evaporation occurs at the free surface of the inside film. The transport equations for momentum and energy are parabolized by the boundary-layer approximation and solved by using the marching technique. The calculation domain of 2 film flow regions (evaporating and condensation films at the inside and outside tube wall respectively) and tube wall is solved simultaneously. The coupling technique for the problem with the 3 different regions and the 2 interfaces of them has been developed to calculate the temperature field. The velocity and temperature fields and the amount of the condensed and evaporated mass as well as the position where the evaporating film is completely dried out are successfully predicted for various inside pressures and inside film inlet flow rates.

열증기압축기 설계와 MED 담수설비에의 적용

박일석(Park Il-Seouk),박상민(Park Sang-Min),하지수(Ha Ji-Soo) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

A thermal vapor compressor in which the subsonic/supersonic flow appears simultaneously, has been accurately designed through the CFD analysis for the various shape parameters such as the primary nozzle shape. converging duct shape. mixing tube diameter. and so on. The performance of the developed thermal vapor compressor has been experimentally verified to be installed in a Multi Effect Desalination(MED) plant as on important element. In this paper. the experimental results for various boundary conditions(motive pressure. suction pressure. and discharge pressure) are presented in comparing with CFD results. The two results show a good agreement with each other within 3.5% accuracy with regard to the entrainment ratio.

냉동 컨테이너 적재부의 배관 형상에 따른 환기성능 실험

박일석(Park Il-Seouk),박상민(Park Sang-Min),이동조(Lee Dong-Jo),설신수(Seol Sin-Su) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

The analysis of ventilation performance varying with duct shapes in reefer container of scale-model has studied experimentally. Most container ships have ventilation system of which ducts extended to<br/> the bottom for the purpose of efficient exhausting of condensing heat from hold. However, the size of ducts is so over-long that it causes manufacturing troubles. In this study, for various types of duct, flow visualization using smoke and normalized temperature analysis are presented. Finally, the cooling performance are compared respectively.