http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
김형대(Hyung Dae Kim),김무환(Moo Hwan Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
‘Nanofluids’ means suspension of common fluids with particles of the order of nanometers in size. The present research is an experimental study of critical heat flux (CHF) behavior in pool boiling of water-TiO₂ nanofluids under atmospheric pressure. CHF for pure water and water-TiO₂ nanofluids were respectively measured using disk-type copper block heater with 10㎜ diameter, and CHF of water with surfactant was also measured to consider the effect of surfactant used to disperse nanoparticle. The results show a large increase in CHF for water-TiO₂ nanofluids compared to pure water. After CHF occurred, heat flux in pool boiling for water-TiO₂ nanofluids was maintained in considerable value, but not for pure water.
나노유체 이용한 풀비등 임계열유속 증가에서 나노입자 유착물의 영향에 관한 실험적 연구
김형대(Hyung Dae Kim),김선태(Seon Tae Kim),안호선(Ho Seon Ahn),김무환(Moo Hwan Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
It has been well known that pool boiling CHF in nanofluids compared to pure water significantly increase due to the deposition of nanoparticles on heater surface. This study concerns the characteristics of the nanoparticle deposition layer and its influence on CHF. Pool boiling experiments were carried out with 0.01.% water-TiO₂ nanofluids to obtain various nanoparticle-deposited heaters. CHF on the prepared heaters was measured during pool boiling in pure water. The heater surfaces were visualized using scanning electron microscope (SEM) and also characterized using contact angle and capillarity. The results showed that the CHF enhancement in nanofluids was completely dependent upon the structural and physicochemical characteristics of the nanoparticle deposition layer.
물-TiO₂ 나노유체 풀비등에서의 임계열유속 증가에 미치는 나노입자의 영향
김형대(Hyung Dae Kim),김정배(Jeong Bae Kim),김무환(Moo Hwan Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
To study the characteristics of CHF (Critical Heat Flux) of nano-fluids, pool boiling CHF experiments of water-TiO₂ nano-fluids were performed with different volume concentrations of titania nanoparticles. The results showed that nano-fluids significantly enhanced CHF compared to pure water. And it was found that nanoparticles were coated on heating surface during pool boiling of nano-fluids. After that, pool boiling CHF of pure water was measured using a nanoparticle-coated heater prepared by pool boiling of nano-fluids on a bare heater. The results showed that CHF enhancement in pool boiling of nano-fluids is mainly caused by the nanoparticle coating of the heating surface.
김형대(Hyung Dae Kim),임윤철(Younchul Rhim) 한국자동차공학회 1992 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this study, the function of a hydraulic brake system with a vacuum <br/> booster is theoretically analyzed according to the mutual relations which follow:<br/> - the brake pedal force vs. booster input force<br/> - the booster output force vs. cylinder input force<br/> - the master cylinder output force vs. hydraulic line pressure<br/> - the hydraulic line pressure vs. braking deceleration.<br/> Also, it is developed a numerical program based on the theory which is able to<br/> predict and analyze the pedal force characteristics at the beginning of the <br/> initial stage of brake system design. Analytical results are compared to the <br/> experimental vehicle test to evaluate the propriety of the theory.<br/>
김형대(Hyung Dae Kim),김무환(Moo Hwan Kim) 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.11
Pool boiling critical heat flux (CHF) of nanofluids with oxide nanoparticles of TiO₂ or Al₂O₃ was experimentally investigated under atmospheric pressure. The results showed that a dispersion of oxide nanoparticles significantly enhances the CHF over that of pure water. Moreover it was found that nanoparticles were seriously deposited on the heater surface during pool boiling of nanofluids. CHF of pure water on a nanoparticle-deposited surface, which is produced during the boiling of nanofluids, was not less than that of nanofluids. The result reveals that the CHF enhancement of nanofluids is absolutely attributed to modification of the heater surface by the nanoparticle deposition. Then, the nanoparticle-deposited surface was characterized with parameters closely related to pool boiling CHF, such as surface roughness, contact angle, and capillary wicking. Finally, reason of the CHF enhancement of nanofluids is discussed based on the changes of the parameters.
나노유체를 이용한 풀비등 임계열유속 증가에 대한 실험적 연구
김형대(Hyung Dae Kim),김무환(Moo Hwan Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Pool boiling CHF performance of aqueous nanofluids was investigated using TiO₂ and Al₂O₃ nanoparticles. The usage of nanofluids as a working fluid could significantly enhance the pool boiling CHF, which was strongly dependent on the kind of nanoparticle as well as the concentration. A nanoparticle surface coating was observed on the heating surface after the experiment and CHF of pure water on the nanoparticle-coated surface was higher than that of nanofluids for all cases. This revealed that the reason of the CHF enhancement using nanofluids existed on the heater surface modified by the nanoparticle deposition. The mechanism of CHF enhancement due to the nanoparticle coating was discussed associated with surface wettability, surface roughness, and maximum capillary wicking height of the nanoparticle-coated surface.
김형대(Hyung Dae Kim),정영훈(Young Hun Jeong),민병권(Byung-Kwon Min) 한국생산제조학회 2005 한국공작기계학회 추계학술대회논문집 Vol.2005 No.-
The electrode wear significantly determinate the machining accuracy in EDM milling. Therefore, the electrode wear need to be identified to improve the machining accuracy. In this regard, a 2D geometric model of micro milling process model was developed considering electrode wear. From the simulation using the developed model, the electrode and workpiece shapes can be predicted. As a result, electrode wear with respect to the amount of workpiece removal can be investigated. Consequently, it is demonstrate that the predicted electrode and workpiece geometries match actual ones well.