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장방형 용기내 자성유체의 Benard유동에 대한 전열 제어 특성에 관한 연구
안종국,서이수,박길문,Ahn, Jong-kug,Seo, Lee-Soo,Park, Gil-Moon 한국유체기계학회 2004 한국유체기계학회 논문집 Vol.20 No.2
This study deals with the Benard Flow of Magnetic Fluids in a rectangular cavity which the ratio between height and width is 1 : 4 and the base side or left side is a heating face while other sides are to be cooling faces. When Magnetic field was equally impressed, considering the internal rotation of the elementary ferromagnetic particle, we found the following result from the numerical analysis of the GSMAC algorithm applied to the equation of the magnetic fluid. Benard flow is controlled by intensity and direction of magnetic fields, and critical point appears when especially magnetic field with a heating base and side area near H=-7000 and H=-10000 is applied.
단순 열전달 모델을 이용한 히트파이프의 열전달 성능 특성에 관한 연구
서재형(Seo, Jae-Hyeong),방유마(Bang, Yu-Ma),서이수(Seo, Lee-Soo),이무연(Lee, Moo-Yeon) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.1
본 연구의 목적은 전기동력 자동차의 전기-전자 장비들을 효과적으로 냉각시키면서 자체적으로 에너지 소비를 최소 화 시킬 수 있는 노력의 일환으로, 단순 열전달 모델을 이용하여 윅이 있는 히트파이프의 열전달 및 유동 특성을 고찰하는 것이다. 이를 위하여 히트파이프는 COMSOL프로그램을 이용하여 해석하였고, 작동유체로 물을 이용하였다. 또한, 히트파이 프의 속도 및 온도 특성을 히프파이프 길이에 따라 해석하였고, 국소 및 평균 Nu수를 계산하였다. 결과적으로, 히트파이프의 관성력은 가열면과 냉각면의 온도차에 의하여 발생하였다. 히트파이프내 열전달은 가열면에서 냉각면으로 발생하고 히트파이프 중앙으로 갈수록 증가하였다. 더불어, 가열면의 Nu수는 최대 4.47로 나타났으며, 평균 Nu수는 1.88이고, 냉각면의 Nu수는 최대 0.7로 나타났으며, 평균 Nu수는 0.1이다. The objective of this study was to examine numerically the heat transfer and flow characteristics of the heat pipe with a wick using the simplified heat transfer model to enhance the cooling effects of high heat flux devices and minimizing the energy consumption for electric vehicles. The heat pipe with a wick was analyzed using commercial software with COMSOL and water was used as the working fluid. The velocity and temperature characteristics of the heat pipe were simulated numerically along the heat pipe and the local and average Nusselt numbers were calculated. As a result, the driving force occurred because of the temperature difference between the hot side and the cold side. The heat transfer of the heat pipe occurred from the hot side to the cold side and increased toward the center position. In addition, the average Nusselt numbers were 1.88 for the hot side and 0.1 for the cold side, and the maximum Nusselt number was 4.47 for the hot side and 0.7 for the cold side.
박정우,유신오,서이수,Park, Joung-Woo,Ryu, Shin-Oh,Seo, Lee-Soo 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.1
In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, vorticity, internal angular momentum and induced magnetization as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter.
자성유체의 밀폐공간내의 열전달 특성에 관한 실험적 연구
박정우(Joung-Woo Park),서이수(Lee-Soo Seo),전철호(Chel-Ho Chen),박길문(Gil-Moon Park) 한국자기학회 2003 韓國磁氣學會誌 Vol.13 No.3
Natural convection of a magnetic fluid is different from that of Newtonian fluids because magnetic-body force exists in addition to gravity and buoyancy. In this paper, natural convection of a magnetic fluids (W-40) in a cubic cavity was examined by experimental method. One side wall was kept at a constant temperature (25℃), and the opposite side wall was also held at a constant but lower temperature (20℃). The magnetic fields of various magnitude were applied up and down by permanent magnets. We measured temperatures at 5 points which are the most suitable places in cavity by the analysis record. The thermo-sensitive liquid crystal film (R20C5A) was utilized in order to visualize wall-temperature distributions. Several kinds of experiments were carried out in order to clarify the influence of direction and intensity of magnetic fields on the natural convection. It was found that the natural convection of a magnetic fluids could be controlled by the direction and intensity of the magnetic fields.
정방형관 내에서 자성유체의 자연대류현상에 대한 수치적 연구
서재형(Jae-Hyeong Seo),이무연(Moo-Yeon Lee),서이수(Lee-Soo Seo) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.7
본 연구에서는 밀폐된 정방형관 내에서 자성유체의 자연대류현상에 대하여 수치해석적으로 접근하였다. GSMAC(Generalized-Simplified Marker and Cell method)법을 이용하여 자성유체의 지배방정식을 풀었으며 외부에서 인가자장의 세기 및 방향에 따른 자연대류현상과 열전달 특성을 수치해석적으로 규명하였다. 자성유체의 자연대류현상은 인가자장의 세기 및 방향에 따라 제어되었다. 자장이 수직방향으로 인가될 경우 자장의 세기 H가 4000일 때 평균 Nusselt 수가 최소가 되었고 자장이 수평방향으로 인가될 경우 자장의 세기 H가 12000일 때 평균 Nusselt 수가 최소가 되었다. 또한, 이 지점을 기준으로 자장의 인가방향과 관계없이 자장의 세기가 증가할수록 평균 Nusselt 수가 증가하였다. This study aims to numerically investigate the natural convection characteristics of a magnetic fluid in a cubic cavity. The governing equations of the magnetic fluid are solved using the Generalized-Simplified Marker and Cell Method (GSMAC). The natural convection and heat transfer characteristics of the magnetic fluid were analyzed by varying the intensity and direction of the magnetic field. As a result, it was found that the natural convection characteristics were controlled by the intensity and direction of the magnetic field, and the mean Nusselt numbers were minimized at a vertical intensity of H=-4000 and horizontal intensity of H=12000 of the magnetic field. In addition, the mean Nusselt numbers increased with the intensities of the magnetic field, regardless of the direction of the magnetic field.
유한요소법을 이용한 자성유체의 거동예측을 위한 수치적 모델링
서재형(Jae-Hyeong Seo),이무연(Moo-Yeon Lee),서이수(Lee-Soo Seo) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.1
The objective of this study is numerically analyzed the behavior characteristics of the magnetic fluid in a closed rectangular container using finite element method (FEM). The governing equations are solved with magnetization and Maxwell equations for consideration of rotating effect of the magnetite particle. Then the discretized equations are solved with boundary conditions of the velocity and temperature. The developed model is validated with the results of Davis (1983) and Fusegi et al. (1991) has a good agreement within 5.5 % and 2.7 %, respectively.
회전수 및 자기장강도 변화에 따른 이중원관내 자성유체의 자연대류 열전달 특성에 관한 실험적 연구
김형진(Hyung-Jin Kim),서재형(Jae-Hyeong Seo),김대완(Dae-Wan Kim),이무연(Moo-Yeon Lee),서이수(Lee-Soo Seo) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.2
The objective of this study is experimentally to investigate natural convective heat transfer characteristics of the ferrofluid for a concentric annuli under rotating magnetic field with variations of the revolution and the magnetic field strength. The rotating magnetic field was provided by induction motor with 6 poles and 3 phases and the revolution and the magnetic field strength were controlled by an inverter driver and a voltage meter, respectively. Temperatures of the inner pipe and the outer pipe in the tested concentric annuli were maintained at 30℃ and 25℃, respectively, during the test and the direction of the rotating magnetic field was a counterclockwise. As a result, the natural convective heat transfer characteristics of the ferrofluid for a concentric annuli were increased with the rise of the revolution and magnetic field strength due to the increased heat dissipation between hot side and cold side of the concentric annuli.
가시화기법을 이용한 고정자장에서 이중원관내 자성유체의 열유동 특성에 관한 연구
김형진(Hyung-Jin Kim),서재형(Jae-Hyeong Seo),김대완(Dae-Wan Kim),이무연(Moo-Yeon Lee),서이수(Lee-Soo Seo) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.1
This article is experimentally to investigate thermal-flow characteristics of the magnetic fluid for concentric annuli under externally fixed magnetic fields using visualization technique. Temperatures of the inner tube and outer tube in the tested concentric annuli were constantly maintained at both 30℃ and 25℃ and the middle tube was filled with the magnetic fluid. Magnetic field was uniformly applied using 4 permanent magnets at 4 directions of the concentric annuli. As a result, the thermal-flow characteristics of the magnetic fluid for concentric annuli could be controlled by directions of the external magnetic fields.
구형 용기 내 자성유체의 슬로싱 특성에 관한 실험적 연구
김대완(Dae-Wan Kim),이무연(Moo-Yeon Lee),서이수(Lee-Soo Seo) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.5
This work describes the experimental investigations on sloshing characteristics of water and ferrofluid as working fluids in the spherical container with the horizontal oscillation motion and compared the results obtained by two working fluids. In order to Investigate the sloshing characteristics of the sphere container with the horizontal oscillation, experiments are performed with the magnetic intensities from 0 mT to 50 mT and horizontal oscillation motions from 5 mm to 15 mm. As results, Ferrofluid without magnetic field in the sphere container showed a similar liquid surface movement with water. The resonance point of the ferrofluid in the sphere container happened at higher value than that of the theoretical resonance frequency with the rise of the magnetic field. In addition, the sloshing characteristics of the ferrofluid in the sphere container can be controlled with the resonance frequency with the magnetic intensity and the liquid surface displacement could be also controlled.