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한태양,손유한,김상열,정현철,김현유,이상로,한준현,Han, Taeyang,Sohn, Youhan,Kim, Sangyeol,Jung, Hyun-Chul,Kim, Hyun You,Lee, San-ro,Han, Jun Hyun 한국재료학회 2018 한국재료학회지 Vol.28 No.12
We investigate the reduction of $SnO_2$ and the generation of syngas($H_2$, CO) using methane($CH_4$) and hydrogen($H_2$) or a mixed gas of methane and hydrogen as a reducing gas. When methane is used as a reducing gas, carbon is formed by the decomposition of methane on the reduced Sn surface, and the amount of generated carbon increases as the amount and time of the supply of methane increases. However, when hydrogen is used as a reducing gas, carbon is not generated. High purity Sn of 99.8 % and a high recovery rate of Sn of 93 % are obtained under all conditions. The effects of reducing gas species and the gas mixing ratio on the purity and recovery of Sn are not significantly different, but hydrogen is somewhat more effective in increasing the purity and recovery rate of Sn than methane. When 1 mole of methane and 1 mole of hydrogen are mixed, a product gas with an $H_2/CO$ value of 2, which is known to be most useful as syngas, is obtained.
마이크로크기 액적의 거동 제어를 통한 액적-점핑 응축 성능 증진
한태양(Taeyang Han),최영현(Younghyun Choi),권정태(Jeong-Tae Kwon),조항진(Hang Jin Jo),김무환(Moo Hwan Kim) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
To increase the efficiency of jumping-droplet condensation, this study proposes a novel surface that promotes coalescence-induced jumping. Inspired the phenomenon in which a growing droplet moves spontaneously within a superhydrophobic V structure, we fabricated nanograssed zigzag structures on the surface to induce spontaneous motion of condensed droplets. The direction of the motion is parallel to the surface, so the condensed droplets easily coalesce on it. Compared to a conventional nanostructured superhydrophobic surface, the proposed surface increased the frequency of coalescence-induced jumping by ≥ 17 times and increased the cumulative volume of jumping droplets by ~ 1.8 times. The proposed surface has great potential to increase the efficiency of various applications that exploit condensation. Furthermore, we expect that the enhanced heat transfer coefficient of jumping-droplet condensation will solve thermal problem of high power electronics, which will be faced with commercialization of 5G.
증발-결정화 방법을 이용한 응축 성능 증진: 자기 배열된 친수성 결정의 효과
한태양(Taeyang Han),최영현(Younghyun Choi),김무환(Moo Hwan Kim),조항진(Hang Jin Jo) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12
Biphilic surfaces having heterogeneous wettability have proved their outstanding condensation efficiency compared to surfaces having homogeneous wettability. However the application of the biphilic surfaces in practical industries is limited due to the difficulty of the fabrication of the surfaces. In this study, we developed a simple and low-cost method to make a biphilic surface using evaporation-crystallization method. The developed surface enhanced the efficiency of condensation by up to 63% compared to a conventional superhydrophobic surface. Furthermore, the evaporation crystallization method induced ‘self-arrangement of hydrophilic crystals’ on a zigzag structured surface. The efficiency of condensation on the zigzag structured surface was increased by 2.4 times using the evaporation-crystallization method. The developed method not only enhanced the condensation efficiency of flat surfaces but also can be applied to complex shapes, increasing the applicability of biphilic surfaces in various industries.
응축 열전달계수 예측을 통한 이종 습윤성을 갖는 액막 채널 표면의 최적설계 및 열전달 성능평가
최영현(Younghyun Choi),한태양(Taeyang Han),정재영(Jaeyoung Jeong),이용남(Yongnam Lee),조항진(HangJin Jo) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
Condensation heat transfer, a heat transfer mechanism utilizing the latent heat, has used in various industrial applications due to its high heat transfer performance. In the case of the dropwise condensation (DWC), the condensate can be quickly removed, so the condensing surface can be exposed to the vapor effectively. This characteristic of DWC is the reason that it has a higher heat transfer coefficient than filmwise condensation (FWC). However, DWC has limitations in use at various applications (e.g. high temperature & pressure) due to the durability issue of the hydrophobic coating layer. To overcome this limitation, at previous study, surface had been developed to enhance heat transfer performance without the hydrophobic coating layer (i.e. water film channeled surface). In this study, prediction of the heat transfer coefficient was carried out to derive the optimal design of this water film channeled surface proposed to increase the heat transfer performance without hydrophobic coating, and heat transfer performance evaluation was performed at pure vapor condition.