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이충구,황춘복,Lee, C.G.,Hwang, C.B. 대한설비공학회 1993 설비공학 논문집 Vol.5 No.4
In this research, unsteady groundwater flow in unconfined and homogeneous three layer aquifers is studied theoretically and experimentally. Numerical solutions are obtained by Runge Kutta and Runge Kutta Gill method after transforming the governing nonlinear partial differential equations to nonlinear ordinary differential equations. Experimental apparatus includes a test section filled with fine, medium and coarse sands. Experimental results are compared with the numerical solutions and both experimental and numerical results correspond well with each other. This numerical approach may be also applied to the cases which have more aquifers.
4각 리브로된 표면조도에 의한 유체유동 및 열전달 증진에 관한 연구
이충구,Lee, C.G. 대한설비공학회 1992 설비공학 논문집 Vol.4 No.3
Theoritical Study is performed on heat transfer and fluid flow induced by square-ribbed roughness elements in a concentric annulus. The fluid properties were assumed to be constant, and the radius($r_m$) of the maximum speed point was found by using the principle of equation of Leung and Labib. The Nusselt number and friction factor as a function of the Reynolds number($R_e=10^4$, $5{\times}10^4$, $7{\times}10^4$, $10^5$) in artifical roughness $S/{\epsilon}=5,10,20,30$, $P/{\epsilon}=2,5,8$ and prandtl number = 0.72 have been discussed. In this study, it has been found that the Nusselt number and friction factor of rough wall are larger than those of smooth ones.
이충구(李忠求) 교수(敎授) 정년퇴임기념특집(停年退任紀念特輯) : 4각 리브로된 표면조도에 의한 우체유동 및 열전달 증진에 관한 연구
이충구 ( C. G. Lee ) 충북대학교 산업과학기술연구소 2010 산업과학기술연구 논문집 Vol.24 No.2
Theoritical Study os performed on heat transfer and fluid folw induced by square-fibbed roughness elements in a concentric annulus, The fluid properteis were assumed to be constant, and the radius(r(m)) of the maximum speed point was found by using the principle of equation of Leung and Llabib. The Nusselt number and friction factor as a function of the Reynolds number(Re=10(4), 5*10(4), 7*10(4), 10(5) in artifical roughness S/e= 5,10,20,30, P/e=2.5.8 and prandtl number=0.72 have been discussed. In this study, it has been found that the Nusselt number and friciton factor of rough wall are larger than those of smooth ones.
기존온수온돌과 조립식 온수온돌의 전열특성에 관한 실험적 연구
민정현,이충구,장문석,Min, J.H.,Lee, C.G.,Jang, M.S. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.4
The objectives of this study are to find out and to analyze the heat transmission characteristics of the conventional and prefabricated Ondol systems. To compare the thermal characteristics of these Ondol, a real sized Ondol model is set in a chamber. Hot water whose temperature is varied from $45^{\circ}C$ to $60^{\circ}C$ with $5^{\circ}C$ interval is supplied to each Ondol system. At that time the temperature distribution of floor surface, the amount of supplied heat, the heat radiation aspect and the heat loss from the floor to the underground are measured and analyzed simultaneously. As a result, even if the supplied hot water temperature to the prefabricated Ondol panel is lower by about $5^{\circ}C$ than that of the conventional Ondol panel, the net radiant effect is same. Heat radiation efficiency of the prefabricated Ondol panel is over 5% better than that of the conventional Ondol panel. It takes 12 hours for the conventional Ondol and 45 minutes for the prefabricated Ondol, respectively to reach steady state.
평판형 히트파이프식 핫척의 표면온도 균일화 향상을 위한 연구
김대현(D. H. Kim),이석호(S. H. Rhi),임택규(T. K. Lim),이충구(C. G. Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
In the precision hot plate for wafer processing, the temperature uniformity of upper plate surface is one of the key factors affecting the quality of wafers. Precision hot plates require temperature variations less than ±1.5% during heating to 120℃. In this study, we have manufactured the flat plate heat pipe hot chuck of circle type(300㎜) and investigated the operating characteristics of flat plate heat pipe hot chuck experimentally. Various liquids(aceton, FC-40, water) were used as the working fluid and charging ratio was changed(14~36 vol.%). Several cases were tested to improve temperature uniformity. Major working fluid to be investigated was water. Using water, various parameters such as charging ratio, wafer operation on-off time, different working fluids. In case of water, the temperature unformity was ±1.5%, response time of wafer were investigated.
비대칭적인 열 및 물질전달이 있는 수직채널에서의 자연대류 해석
태춘섭,이충구 충북대학교 건설기술연구소 1998 建設技術論文集 Vol.17 No.1
This study aims to investigate theoretically the role of heat and mass transfer, in connection with the vaporisation of thin liquid film on the lower girt of inside channel, in natural convection flows driven by the buoyancy forces of thermal and mass diffusion. The upper surface provides a uniform heat flux, though asymmetric. The FDM(Finite Difference Method) was used to solve the governing equations of laminar natural connective channel flow. The relationship between the dimensionless flow rate and Grashof number was presented graphically in terms of the ratio of wet- or dry-pant channel length to the heated length. The result of this study elucidated the important role of liquid film in laminar natural connective flows.