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전단박화유체의 수직상향 난류유동시 저항감소에 관한 연구
차경옥,김봉각,김재근,Cha, Kyong-Ok,Kim, Bong-gag,Kim, Jea-Geun 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.12
The drag reduction is the phenomenon that occurs only when the shear stress from the wall of pipe is beyond the critical point. The drag reduction increase as the molecular weight, concentration of the polymer and Reynolds number increase, but it is limited by Virk's maximum drag reduction asymptote. Because of the strong shear force for the polymer on the turbulent flow, the molecular weight and the drag reduction do not decrease. Such mechanical degradation of the polymer occurs in all polymer solvent systems. This paper is to identify and develop high performance polymer additives for fluid transportations with the benefits of turbulent drag reduction. In addition, drag reduction in vertical flow by measuring the pressure drop and local void fraction on vertical-up flow of close system is evaluated.
김진현,차경옥 明知大學校 産業技術硏究所 2002 産業技術硏究所論文集 Vol.21 No.-
Cooling is therefore normally achieved through a balance of rant and fan action. Coolant is used to cool the engine's radiator and turbocharger intercooler in order to provide suitable temperatures, which result in higher power, better fuel economy, improved emissions and extended engine life. There are a variety of cooling systems that can be used to accomplish this goal. More recently additional large heat loads hate been imposed and fan site had to be increased. To reduce the associated increase in noise and to achieve a better match for engine-drive fans between the cooling air flow under ram conditions and the heat load generated by the engine, various means were devised to modulate the fan's output, or to decouple th e fan from the engine. Present emphasis on improved fuel economy has created a new urgency to make cooling systems more compact and efficient. This paper studies the various conditions and analyze the heat exchanger's capabilities and cooling effectiveness for several air flowrates, based on a typical automotive engine.
차량용 배기계의 맥동압력으로 인한 도출음과 방사음에 관한 실험적 연구
김명균,이준서,차경옥 명지대학교 산업기술연구소 2001 産業技術硏究所論文集 Vol.20 No.-
In exhaust system, internal pulsating pressure and shell vibration greatly affect the exhaust noise and the (surface) radiated noise. This noise is emitted from the tailpipe outlet and the muffler outer wall due to the pulsation of the exhaust gas pressure. This paper describes and analytical study of these characteristics as influenced by exhaust system structure. An exhaust system simulator was used for generating the pressure pulsation. The relationship between pulsating pressure and shell vibration was analyzed. The relationship between the exhaust noise and surface radiated noised was also analyzed.
金鎭玄,李海喆,車京玉 明知大學校 産業技術硏究所 2007 産業技術硏究所論文集 Vol.26 No.-
As a material for a diesel particulate filter, metal foam shows better mechanical and thermal characteristics than ceramic. So the feasibility of metal foam filters were investigated in DPF(diesel particulate filter trap) system in this study. Three proto type DPFs using the pure nickel foam filter and nickel alloy(INCONEL 625) foam were tested. The characteristics of back pressure, PM mass and nano-particle reduction performance were compared with those with wall flow type filter at the various engine operation conditions. It was confirmed that metal foam filters have a possibility for the application in DPF system.
비뉴톤유체에 의한 효율적인 열관리 및 저항감소에 관한 실험적 연구
차경옥,김재근 明知大學校 産業技術硏究所 2000 産業技術硏究所論文集 Vol.19 No.-
When water soluble polymer is applied to various kinds of fluid transportation systems, it is predicted that the application could be used for the progress of pump capacity and so forth in the fluid transportation. But in the condition of the poorly evolved theories concerning the development of turbulence in the turbulent flow of the viscosity fluid and the dynamics of polymer, actually it is very difficult to develop the fixed quantity analysis. When polymer is also flowing in the fluid transportation system, the degradation which has very close relation with the phenomena of drag reduction occurs necessarily. This study has been focussing on a searching examination for the experimental study considering the mechanical degradation and the thermal degradation in the closed system to find out the conditions which could improve the pump capacity in the heat union electric power plant and so on.