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방사광 X-선 영상법을 활용한 구조표면에서의 모세관유도흐름과 임계열유속에 대한 가시화 연구
곽호재(H. J. Kwak),유동인(D. I. Yu),노현우(H. Noh),박현선(H. S. Park),김무환(M. H. Kim) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
Over the past several decades, phenomena related to critical heat flux (CHF) on structured surfaces have received a large amount of attention from the research community. The purpose of such research has been to enhance the safety and efficiency of a variety of thermal systems. A number of theories have been put forward to explain the key CHF enhancement mechanisms on structured surfaces. However, these theories have not been confirmed experimentally due to limitations in the available visualization techniques and the complexity of the phenomena. To overcome the limitations of the previous visualization techniques and elucidate the CHF enhancement mechanism on the structured surfaces, we introduce synchrotron X-ray imaging with high spatial (~2 um) and time (~20000 Hz) resolutions. This technique has enabled us to confirm that capillary-induced flow is the key CHF enhancement mechanism on structured surfaces.
방사광 X-선 영상법을 활용한 마이크로/나노 구조 표면에서의 액체 퍼짐 가시화 연구
곽호재(H. J. Kwak),유동인(D. I. Yu),도승우(S. W. Doh),박현선(H. S. Park),김무환(M. H. Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
In these days, nano/micro technology has been applied to improve the solid surface wettability. Also, last researches indicate that nano structures can improve the surface wettability in the hydro-philic direction and the liquid spreading (propagation) is generated by capillary wicking. Most of the research shows qualitative analysis of the spreading phenomena due to the difficulty of small scale analysis (nano structure). In this research, quantitative analysis of the droplet interfacial behavior on silicon surfaces with micro/nano/micro-nano structures are experimentally investigated. The interfacial behavior is directly visualized by synchrotron X-ray imaging(side view). On the structured surfaces, spreading phenomena was occurred and the behaviors of liquid interface on the surfaces are different. The liquid propagation is enhaced when micro structure is combined with nano structure. Through the experiment, we understand the phenomena of liquid propagation and diffusion with the surface geometrical characteristics.
마이크로-나노 구조가 있는 표면에서의 액적 계면 거동 현상에 대한 연구
곽호재(H. J. Kwak),유동인(D. I. Yu),안호선(H. S. Ahn),김동억(D. E. Kim),박현선(H. S. Park),키요후미 모리야마(K. Moriyama),김무환(M. H. Kim) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Recently, to enhance the wetting characteristics of the surfaces, the hierarchical surfaces with micro and nano structures are intensively focused in the various research and engineering fields. On the hydrophilic surface with hierarchical structures, the super-hydrophilic surfaces are generally characterized by the interfacial behavior of water droplet. In this study, the interfacial behavior is experimentally investigated. Using the dry etching and conventional lithography method, the quantitative hierarchical surfaces are developed. The movement of the liquid-vapor interface on the test sections is visualized by the high speed camera. On the basis of the visualized data, the interfacial behavior of water droplet is intensively investigated according to the surface geometrical characteristics.
마이크로 구조가 있는 친수성/소수성 표면에서의 젖음성 및 액적 증발 현상에 대한 연구
유동인(D. I. Yu),곽호재(H. J. Kwak),도승우(S. W. Doh),강희찬(H. C. Kang),안호선(H. S. Ahn),박현선(H. S. Park),키요후미 모리야마(K. Moriyama),김무환(M. H. Kim) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
According to the surface condition, the droplet has the contact angle and it is complexly evaporated. Therefore, the evaporation phenomena of the water droplet on the surface should be analyzed on the basis of the wetting phenomena. In this study, it is investigated the wetting and evaporation phenomena of water droplet on the textured hydrophilic / hydrophobic surfaces. On the well-defined surfaces about the surface condition, the apparent contact angle is precisely measured. To compare between experimental data and the previous wetting models, the models are experimentally validated. Subsequently, to study the evaporation phenomena, the contact angle and diameter are measured during droplet evaporation. On the basis of the wetting phenomena, the evaporation performance is analyzed depending on the surface conditions.