거친 사각채널에서 열전달과 유체유동 특성에 관한 실험 및 수치해석

강호근,배성택,이대희,안수환,Kang, Ho-Keun,Baer, Sung-Taek,Lee, Dae-Hee,Ahn, Soo-Whan 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.2

Experiment and three dimensional numerical investigations of incompressible turbulent flow through square channels with one- and two-sided ribbed walls are performed to determine pressure drop and heat transfer. The CFX(version 5.7) software package is used for the computation. The ribbed walls have a $45^{\circ}$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The numerical results coincide with experimental data that obtained for $7,600{\le}Re{\le}24.900$, the pitch-to-rib height ratio (p/e) of 8.0. and the rib height-to-channel hydraulic diameter ratio ($e/D_h$) of 0.0667. The results show that values of local heat transfer coefficient and friction factor in the channel with two-sided ribbed wall are higher than those in the channel with one-sided ribbed walls.

An Examination on the Dispersion Characteristics of Boil-off Gas in Vent Mast Exit of Membrane Type LNG Carriers

강호근,Kang, Ho-Keun The Korean Society of Marine Environment and safet 2013 해양환경안전학회지 Vol.19 No.2

일반적으로 액체가스운반선은 인화성 화물이나 독성물질을 운반한다. 이러한 화물들은 폭발, 화재 및 인명손상을 가져올 수 있기 때문에, 액체가스운반선의 거주구역, 서비스 구역 및 통제실은 가스의 유입이 원천적으로 차단되도록 설계한다. 이러한 이유로, IMO IGC 코드의 멤브레인형 LNG선박의 화물탱크에 설치되는 벤트 출구의 높이는 노출갑판상 B/3 또는 6m 중 큰 것 이상으로 하고 작업구역 및 전후부 통행로, 갑판상의 저장탱크 및 화물설계 액위보다 6m 이상 높게 설치하여야 한다라고 규정하고 있다. 또한 LNG 시장이 점진적으로 증가하면서, LNG선박의 크기도 증가해 왔다. 때문에 현 규정에 의하면 LNG선박의 벤트의 높이는 선박 폭(B)에 비례하기 때문에 상당히 높아져야 할 것이며, 이는 높은 벤트 마스트(Mast)로 인하여 작업의 어려움 및 전방 시야를 방해하는 등 항해의 어려움을 초래한다. 본 연구에서는 멤브레인형 LNG선의 Sea-trial시에 측정하였던 데이터 및 CFD유동해석을 통해 LNG선박 화물탱크의 벤트 출구의 높이에 대한 적합성 평가를 수행한다. Liquefied gas carriers generally transport cargoes of flammable or toxic nature. Since these cargoes may cause an explosion, fire or human casualty, the accommodation spaces, service spaces and control stations of liquefied gas carriers should be so located as to avoid ingress of gas. For this reason, the paragraph 8.2.9 of IGC Code in IMO requires that the height of vent exits should be not less than B/3 or 6 m whichever is greater, above the weather deck and 6 m above the working area and the fore and aft gangway to prevent any concentration of cargo vapor or gas at such spaces. Besides as known, the LNG market has been growing continually, which has led to LNG carriers becoming larger in size. Under this trend, the height of a vent will have to be raised considerably since the height of a vent pipe is generally decided by a breadth of a corresponding vessel. Accordingly, we have initiated an examination to find an alternative method which can be used to determine the safe height of vent masts, instead of the current rule requirement. This paper describes the dispersion characteristics of boil-off gas spouted from a vent mast under cargo tank cool-down conditions in the membrane type LNG carriers.

BEMT를 적용한 20kW 수평축 풍력터빈 형상설계 및 성능해석

강호근,남청도,이영호,김범석,Kang, Ho-Keun,Nam, Cheong-Do,Lee, Young-Ho,Kim, Beom-Seok 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.6

The optimum design and the performance analysis software called POSEIDON for the HAWT (Horizontal Axis Wind Turbine) is developed by use of BEMT, which is the standard computational technique for prediction of power curves of wind turbines. The Prandtl's tip loss theory is adopted to consider the blade tip loss. The lift and the drag coefficient of S-809 airfoil are predicted via X-FOIL and the post stall characteristics of S-809 also are estimated by the Viterna's equations.$^{[13]}$ All the predicted aerodynamic characteristics are fairly well agreed with the wind tunnel test results. performed by Sommers in Delft university of technology. The rated power of the testing rotor is 20kW(FIL-20) at design conditions. The experimental aerodynamic parameters and the X-FOIL data are used for the power Prediction of the FIL-20 respectively The comparison results shows good agreement in power prediction.

내부자유도를 갖는 차분래티스볼츠만 모델에 의한 에지톤의 수치계산

강호근,김은라,오세경,Kang Ho-Keun,Kim Eun-Ra,Oh Se-Kyung 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.8

A lattice BGK model based on a finite difference scheme with an internal degree of freedom is employed and it is shown that a diatomic 9as such as air is successfully simulated In a weak compressive wane problem and Coutte flow, the validity and characteristics of the applied model are examined. With the model. furthermore. we present a 2-dimensional edge tones to predict the frequency characteristics of discrete oscillations of a jet-edge feedback cycle by the FDLB model (I.D.F FDLBM) in which any specific heat ratio $\gamma$ can be chosen freely. The jet is chosen long enough in order to guaranteed the Parabolic velocity profile of a jet at the outlet. and the edges have of an angle of $\alpha$=$23^{0}$ and $20^{0}$. A sinuous instability wane with real frequency resulting from Periodic oscillation of the jet around the edge is propagated on the upper and lower of wedge.

차분 래티스볼츠만법에 Subgrid 난류모델의 적용

강호근,안수환,김정환,Kang Ho-Keun,Ahn Soo-Whan,Kim Jeong-Whan 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.5

Two-dimensional turbulent flows past a square cylinder and cavity noise are simulated by the finite difference lattice Boltzmann method with subgrid turbulence model. The method, based on the standard Smagorinsky subgrid model and a single-time relaxation lattice Boltzmann method, incorporates the advantages of FDLBM for handling arbitrary boundaries. The results are compared with those by the experiments carried out by Noda & Nakayama and Lyn et al. Numerical results agree with the experimental ones. Besides, 2D computation of the cavity noise generated by flow over a cavity at a Mach number of 0.1 and a Reynolds number based on cavity depth of 5000 is calculated. The computation result is well presented a understanding of the physical phenomenon of tonal noise occurred primarily by well-jet shear layer and vortex shedding and an aeroacoustic feedback loop.

사각채널에서 설치된 배플에 의한 열전달 거동에 관한 실험 및 수치해석

강호근(Ho Keun Kang),안수환(Soo Whan Ahn),배성택(Sung Taek Bae) 한국마린엔지니어링학회 2006 한국마린엔지니어링학회 학술대회 논문집 Vol.2006 No.-

Experimental and numerical analysis on the heat transfer behaviors and the associated frictional loss in a rectangular channel with two inclined perforated baffles(u 5°) mounted on the bottom plate has been systematically performed. The parametric effects of perforated baffles (3, 6, 9 holes) and flow Reynolds number on heat transfer characteristics of the heated target surface are explored. A combination of two baffles of same overall size was considered and the flow Reynolds number for this study is varied between 28,900 and 61,800. Comparisons of the experimental data with the numerical results by commercial code CFX 5.7 are made. As for the investigation of heat transfer behaviors on local Nusselt number with the two baffles installed at x/D<SUB>h</SUB>=0.8 and x/D<SUB>h</SUB>=8.0, it is evident that there exist an optimum perforation density to maximize heat transfer coefficients; i.e., the maximum Nusselt number decreases with increasing number of holes.

차분격자볼츠만법에 의한 Edge음의 직접계산

강호근(Ho-Keun Kang),김유택(Yu-Taek Kim),이영호(Young-Ho Lee) 한국유체기계학회 2003 유체기계 연구개발 발표회 논문집 Vol.- No.-

Two-dimensional direct numerical simulation of the edge-tones by the finite difference lattice Boltzmann method (FDLBM) is presented. We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted coordinates. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. It is clarified that the sound wave generated in rather wide region and individual vortices do not affect the sound wave propagation.

차분 격자볼츠만법을 이용한 유체음의 특성에 관한 수치계산

강호근(Ho-Keun Kang),노기덕(Ki-Deok Ro),손영태(Yeong-Tae Son),이영호(Young-Ho Lee) 대한기계학회 2002 대한기계학회 기타 간행물 Vol.2002 No.11

Twisted Tape가 설치된 사각 덕트에서 스월유동 및 코너효과가 미치는 열전달 성능

강호근(Ho-Keun Kang),B.K.P Ary,안수환(Soo-Whan Ahn),최종웅(Jong-Woong Choi) 한국마린엔지니어링학회 2008 한국마린엔지니어링학회 학술대회 논문집 Vol.2008 No.-

This paper presents numerical and experimental predictions of characteristics of turbulent flow, heat transfer and friction factors in a square sectioned duct (30 × 30㎜) with twisted tape inserts and with twisted tape inserts plus rib tubulators. Turbulent swirl flows having Reynolds numbers ranging from 8,900 to 29,000, a rib height-to-channel hydraulic diameter (e/Dh) of 0.067, and a length-to hydraulic diameter (L/Dh) of 30, are considered. The rib tubulators are arranged to follow the trace of the twisted tape and along the flow direction. The twisted tape is 0.1㎜ thick carbon steel sheet with diameter of 28㎜, length of 900㎜, and 2.5 turns. Each wall is composed of isolated aluminum sections. Two heating conditions are applied for four side walls and two opposite walls. The correlation for friction factor and Nusselt number are derived from the predicted data. The results show that uneven surface heating enhances the heat transfer coefficient over uniform heating condition, and significant improvements can be achieved with twisted tape inserts plus interrupted ribs.

사각 덕트 내에 설치된 2개의 경사진 배플에 의한 열전달 증진 효과에 관한 실험 및 수치해석

강호근(Ho-Keun Kang),안수환(Soo-Whan Ahn),Ary Bachtiar Krishna Putra 대한설비공학회 2007 설비공학 논문집 Vol.19 No.11

Baffles enhance heat transfer by disturbing boundary layer and bulk flow, creating impingement, and increasing heat transfer surface area. This study was performed to determine how the two inclined baffles (α = 5° perforated models) placed at a rectangular channel affect heat transfer and associated friction characteristics. The parametric effects of perforated baffles (3, 6 and 12 holes) and flow Reynolds number ranging from 28,900 to 61,800 on the heated target surface are explored. Comparisons of the experimental data with the numerical results by commercial code CFX 10.0 are presented. As for the investigation of heat transfer behaviors on local Nusselt number with two baffles placed at χ/Dh = 0.8 and χ/Dh = 8.0 of the edge of baffles, it is evident that the inclined perforated baffles augment overall heat transfer significantly by both jet impingement and boundary layer separation. There exists an optimum perforation density to maximize heat transfer coefficients i.e., the average Nusselt number increases with increasing number of holes, but the friction factor decreases with an increase in the hole number placed at baffles.