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과도 액정 기법을 이용한 와동발생기 하류의 유동장 및 열전달 측정
홍철현,양장식,이기백,Hong, Cheol-Hyun,Yang, Jang-Sik,Lee, Ki-Baik 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.11
The effects of the interaction between flow field and heat transfer caused by the longitudinal vortices are experimentally investigated using a five hole probe and a transient liquid crystal technique. The test facility consists of a wind tunnel with vortex generators protruding from a bottom surface and a mesh heater. In order to control the strength of the longitudinal vortices, the angle of attack of vortex generators used in the present experiment is 20$^{\circ}$, and the spacing between the vortex generators is 25mm. The height and cord length of the vortex generator is 20mm and 50mm, respectively. Three-component mean velocity measurements are made using a f-hole probe system, and the surface temperature distribution is measured by the hue capturing method using a transient liquid crystal technique. The transient liquid crystal technique in measuring heat transfer has become one of the most effective ways in determining the full surface distributions of heat transfer coefficients. The key point of this technique is to convert the inlet flow temperature into an exponential temperature profile using the mesh heater set up in the wind tunnel. The conclusions obtained in the present experiment are as follows: The two maximum heat transfer values exist over the whole domain, and as the longitudinal vortices move to the farther downstream region, these peak values show the decreasing trends. These trends are also observed in the experimental results of other researchers to have used the uniform heat flux method.
홍철현,이기백,양장식,Hong Cheol-Hyun,Lee Ki-Baik,Yang Jang-Sik 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.1
A transient liquid crystal technique has become one of the most effective ways in measuring the local heat transfer coefficients on the entire surface. The key Point of this technique is to convert the inlet flow temperature into an exponential temperature profile using a mesh heater. In order to verify the validity of this technique. the heat transfer characteristics on the wall surface by a pair of longitudinal vortices is investigated experimently and numerically. A standard ${\kappa}-{\varepsilon}$ is used for the numerical analysis of turbulent flow field. It is found from experiment and numerical analysis that two peak values exist over the whole domain. as the longitudinal vortices move to the farther downstream. these peak values decrease and the dimensionless averaged Nusselt number with the lapse of time is maintained nearly at constant values. The experiment results obtained from the present experiment in terms of the transient liquid crystal technique are in good agreement with the numerical results. Therefore, the transient liquid crystal technique developed for the measurement of heat transfer coefficient is proved to be a valid method.
대형 풍력 발전용 필라멘트 와인딩 복합재 타워의 고유 진동수 해석에 관한 연구
홍철현(Cheol-Hyun Hong) 한국해양공학회 2011 韓國海洋工學會誌 Vol.25 No.2
The purpose of this study was to investigate the natural frequency of filament-wound composite towers for large scale wind-turbines using the finite element method (FEM). To define the material properties, we used both the effective property method and the stacking properties method. The effective properties method assumes that a composite consists of one ply. The stacking properties method assumes that a composite consists of several stacked plies. First, a modal analysis of the tower, filament-wound with angles of [±30], was carried out using the two methods for composite material properties, the stacking method and effective method. Then, an FE analysis was performed for composite towers using filament winding angles of [±30], [±45], and [±60]. The FE analysis results using the stacking properties of the composite were in good agreement with the results from the effective properties method. The difference between the FEM and material properties methods was approximately 0~0.6%.
복합재를 이용한 대형 풍력 발전용 타워 개발에 관한 연구
홍철현(Cheol-Hyun Hong),한정영(Jeong-Young Han),정재훈(Jae-Hun Jeong),강병윤(Byong-Yun Kang),문병영(Byung-Young Moon) 한국유체기계학회 2011 유체기계 연구개발 발표회 논문집 Vol.2011 No.11
Wind turbine tower will be required to be lighter, more reliable and more consistent. Therefore it is necessary to lose weight of the wind turbine tower. This points squarely toward hybrid/composite tower production growing. It is important to note however that hybrid/composite tower production as it is today is flawed and that there are ways to improve greatly on the performance of these towers in manufacturing process and in their in-service performance. Through this, we have some detail on the current process and its advantage of cost and weight of towers.
다구찌 기법을 이용한 윈드실드 수직축 풍력 터빈의 기초 실험 연구
홍철현(Cheol-Hyun Hong),서성호(Seong-Ho Seo) 한국해양공학회 2011 韓國海洋工學會誌 Vol.25 No.3
This study aimed to develop a wind turbine system for the domestic wind environments. The Taguchi method was applied to obtain the optimal design for a wind turbine with a wind-shield. The design parameters were defined to look for the shape of the wind turbine. Optimal parameters were determined on the basis of the analyzed level averages of the characteristics. According to the test results to which the optimal parameters were applied, the rpm improved. It was also found that a windshield 3/4 the size contributes to improving the efficiency of existing turbines.
경량화 복합재를 이용한 풍력 블레이드 개발과 해석에 관한 연구
강병윤,한정영,홍철현,문병영,Kang, Byong-Yun,Han, Jeong-Young,Hong, Cheol-Hyun,Moon, Byung-Young 한국유체기계학회 2011 한국유체기계학회 논문집 Vol.19 No.6
Wind turbine blades will be required to be longer, lighter, more reliable and more consistent. Therefore it is necessary to lose weight of the wind turbine blades. This points squarely toward prepreg blade production growing. It is important to note however that prepreg blade production as it is today is flawed and that there are ways to improve greatly on the performance of these blades in manufacturing process and in their in-service performance. Through this, we have some detail on the current process and its advantage of cost and weight of blades.