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RISS 인기검색어
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- 저자 : 김영찬 ( Yeung Chan Kim ) (검색결과 37 건)
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김영찬 ( Yeung Chan Kim ) 한국분무공학회 2014 한국액체미립화학회지 Vol.19 No.1
In the present study, experiment on the evaporation of pure water droplet on heated surface was conducted, and the evaporative heat transfer coefficients were calculated from experimental results. The pure water droplet of about 10 μl was applied onto the heat transfer surface, then the shape of the droplet was analyzed during the evaporation. In addition, the effect of surface roughness on the evaporative heat transfer was also investigated. Experimental results showed that the evaporative heat transfer coefficients increased rapidly along with the increase of surface temperature and the heat transfer coefficients increased with the increase of surface roughness.
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김영찬(Yeung Chan Kim) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.3
본 연구에서는 액적유량밀도가 0.00002~0.003㎥/(㎡s)인 분무영역을 대상으로 핵비등영역과 막비등 영역에서의 분무냉각 열유속을 측정하여 비등곡선을 완성함과 동시에 액적유량밀도가 분무냉각 비등곡선에 미치는 영향을 실험적으로 파악하였다. 실험결과로부터 액적유량밀도가 증가할수록 비등곡선 전체영역에서 분무냉각 열유속이 증가하고 있음을 알 수 있었다. 특히 액적유량밀도가 증가함에 따라 막비등영역의 열유속보다 CHF부근의 핵비등영역에서의 열유속이 큰 폭으로 증가함을 알 수 있었으며, 이는 액적유량에 의한 상변화 열전달의 효과가 핵비등영역에서 더욱 크게 나타나고 있는 것으로 판단된다. 본 연구범위에서 액적의 온도가 증가할수록 막비등영역에서의 열유속은 약간 감소하지만, 핵비등영역 또는 CHF에 있어서 액적의 온도에 의한 영향은 거의 없는 것으로 나타났다. The heat flux of spray cooling in nucleate boiling and film boiling region were experimentally investigated under the experimental condition that the droplet flow rate is in the range 0.00002 ㎥/(㎡s)-0.003㎥/(㎡s). The following results were obtained. The heat flux of spray cooling increased with increasing droplet flow rate in both surface temperature regions of nucleate boiling and film boiling. Particularly, the heat flux of the nucleate boiling region, including CHF, increased more greatly. This experimental result indicates that for nucleate boiling, the effect of phase-change heat transfer by droplet flow rate was more remarkably apparent compared to film boiling. However, the effect of droplet temperature on the heat flux of spray cooling appeared unclear in both surface temperature regions.
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김영찬 ( Yeung Chan Kim ) 한국액체미립화학회 2018 한국액체미립화학회지 Vol.23 No.3
The critical heat flux of spray cooling were measured on the test surface of 10 mm diameter made by stainless steel. The experiments were carried out for the droplet-flow-rate of 0.00002~0.003 ㎥/(㎡s) and liquid subcooling temperature of 40~75℃. Experimental results showed that the critical heat flux of spray cooling increased remarkably with the increase of droplet-flow-rate. Meanwhile, the effect of liquid subcooling on critical heat flux of spray cooling appeared weakly under the present experimental conditions. In additions, correlation between the dimensionless critical heat flux and Weber number based on droplet-floe-rate was developed for experimental results.
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김영찬(Yeung Chan Kim) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.7
본 연구에서는 산화구리(CuO) 나노분말과 순수 물을 혼합하여 제조한 나노유체를 이용하여 가열된 고체표면에 있어서 나노유체 액적의 증발특성에 대한 실험적 연구를 수행하였다. 실험결과로부터 가열된 표면에서 나노유체 액적의 증발속도는 순수 물 액적보다 증발속도가 약간 증가하는 경향이 있음을 알 수 있었으며, 이는 나노유체에 포함된 나노입자가 유체의 열전도도를 향상시켜 고체 표면에서 액적으로의 열전달이 촉진되었기 때문인 것으로 판단된다. 또한 고체의 표면조도가 커질수록 액적의 증발속도가 약간 증가하였으며, 이는 고체의 표면조도가 커질수록 고체-액체의 접촉 면적이 증가하여 열전달이 촉진되었기 때문인 것으로 추정된다. The evaporation characteristics of nanofluid droplets on a heated solid surface were experimentally investigated. The experiments were conducted using pure water and a nanofluid of water mixed with CuO nanoparticles, and the solid surface was made of a copper block heated by a nine cartridge heater. The experimental results showed that the evaporation rate of the nanofluid droplet was higher than that of the pure water droplet on the heated solid surface because nanoparticles increased the thermal conductivity of the nanofluid. Furthermore, it was found that the evaporation rate of the nanofluid droplet increased with the solid surface roughness. This may be because the actual area of the liquid-solid interface increased with the solid surface roughness.
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김영찬(Yeung Chan Kim) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.6
본 연구에서는 고체의 표면조도가 나노유체 액적의 접촉각에 미치는 영향에 대해 실험적 연구를 수행하였다. 나노유체는 산화구리(CuO) 나노분말을 순수 물과 혼합하여 제조하였으며, 고체는 한 변의 길이가 10㎜ 정육면체 구리시편을 실험에 사용하였다. 나노유체 액적의 접촉각은 동일한 표면조도 조건에서 순수 물 액적의 접촉각 보다 다소 낮게 측정되었으며, 구리시편의 표면조도가 증가할수록 순수 물과 나노유체 액적의 접촉각은 모두 증가하고 있음을 실험결과로부터 알 수 있었다. 또한 가열-급냉(quench) 실험을 거친 구리시편 표면에서의 접촉각은 순수 표면에서의 접촉각보다 다소 낮게 측정되었으며, 이는 구리표면의 산화에 기인하는 것으로 판단된다. 그러나 가열-급냉 실험에 있어서 냉각 액체로서 순수 물과 나노유체를 사용한 경우의 액적 접촉각 측정결과들은 큰 차이가 없는 것으로 나타났으며, 이러한 실험결과로부터 냉각과정에 있어서 나노입자가 액적의 접촉각에 영향을 미칠 정도로 구리시편의 표면상태를 변화시키지 못하는 것으로 생각된다. The effects of solid surface roughness on the contact angle of a nanofluid droplet were experimentally investigated. The experiments were conducted using the solid surface of a 10 mm cubic copper block and the nanofluid of water mixed with CuO nanoparticles. The experimental results showed that the contact angles of nanofluid droplets were lower than those of water droplets and that the contact angle of the nanofluid droplet increased with the solid surface roughness. Furthermore, it was found that the contact angles of water droplets on the solid surface quenched by both water and the nanofluid were lower than those of water droplets on the pure solid surface. However, significant differences were not observed between the contact angles on the solid surfaces quenched by water and the nanofluid.
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액적 유량과 분무냉각 막비등 열전달의 상관관계에 관한 연구
김영찬(Yeung-Chan Kim),윤승민(Seung-Min Yun) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
A new correlation between the Nusselt number based on modified heat transfer coefficient and Reynold number based on droplet-flow-rate was developed for the experimental data of the previous reports. The modified heat transfer coefficient was defined as ratio of wall heat flux to droplet subcooling. In the previous reports, the local heat flux of spray cooling in the film boiling region were experimentally investigated for the water spray region of D<SUB>max</SUB> = 0.0007~0.03㎥/(㎡s). In the region near the stagnation point of spray flow, a new heat transfer correlation is recommended which shows good predictions for the water spray region of D<SUB>x</SUB>≤0.01㎥/(㎡s).
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물-공기 원추형 분무시스템에 있어서 분무냉각 막비등 열전달에 관한 연구
김영찬(Yeung-Chan Kim),윤승민(Seung-Min Yun) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The local heat flux of spray cooling in the film boiling region were experimentally investigated for the spray region of D<SUB>max</SUB> = 0.005~0.03 ㎥/(㎡s). A twin-fluid full cone spray nozzle was employed for the experiment and the distributions of droplet flow rates were obtained for air-water full cone sprays. A stainless steel block was cooled down from initial temperature of about 800℃ by full cone spray. In the region near the stagnation point, it was found from the experimental results that the experimental data are in good agreement with the results predicted from the correlations between the local heat transfer and the local droplet flow rate proposed in the previous report [1]. However, it was found that the experimental data of Dr 0.01 ㎥/(㎡s) are a little smaller than the results predicted from the correlations.
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