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RISS 인기검색어
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- 저자 : 서동현(DongHyun Seo) (검색결과 58 건)
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발수 코팅의 균일성에 따른 응축 거동 및 열전달 성능에 관한 연구
서동현(Donghyun Seo),심재환(Jaehwan Shim),남영석(Youngsuk Nam) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
In this work, we fabricate superhydrophobic tube type condensers and investigate the condensation heat transfer performance. Using a well-controlled environmental chamger, a wide range of supersaturation level was achieved with minimizing non-condensable effects. We show that the supersaturation level has a significant effect on the condensate mobility and resulting heat transfer performance especially for the superhydrophobic condensers. Particularly, it is demonstrated that quality of the hydrophobic coating on the superhydrophobic surface significantly determins condensation behavior and resulting condensation heat transfer performance. This work will help optimize the surface condition of condensers operating at practical supersaturation level.
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초발수 표면 위 마이크로 구조물의 기하학적 패턴에 따른 물 수집 성능의 영향
서동현(Donghyun Seo),이충엽(Choongyeop Lee),남영석(Youngsuk Nam) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
On superhydrophobic (SHPo) surfaces, either of two wetting states ?the Cassie state (i.e., non-wetted state) and the Wenzel state (i.e., wetted state) ? can be observed depending on the thermodynamic energy of each state and experimental conditions. Each wetting state leads to quite a distinctive dynamic characteristic of the liquid drop on SHPo surfaces and it has been of primary interest to understand or induce the desirable wetting state for relevant thermofluid engineering applications. In this study, we investigate how the wetting state of microstructured SHPo surfaces influences water harvesting performance of the SHPo surface via dewing by testing two different surface patterns of posts and grates with varying structural parameters. On grates, the observed wetting state during condensation is well described by the thermodynamic energy criteria and it is seen that the Cassie state is associated with the faster removal of smaller droplets due to the higher drop mobility compared with the Wenzel state. Meanwhile, on posts, the observed wetting state is dominantly the Wenzel state regardless of the thermodynamic energy of each state, and due to much larger pinning force of the Wenzel state the condensates are shed slowly only after they grow to a sufficiently large size. Based on a simple modeling, we attribute this difference in the droplet shedding characteristics to the different dynamic pathway from the Wenzel state to the Cassie state between posts and grates. Overall, the faster drop removal on the SHPo surface helps enhance the water harvesting performance of the SHPo surfaces by facilitating the condensation on the droplet-free area, as manifested by the best water harvesting performance of gratings on the Cassie state amongst the tested surfaces.
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서동현(Donghyun Seo),오승태(Seungtae Oh),이충엽(Choongyeop Lee),남영석(Youngsuk Nam) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
Frost formation and accumulation have widely caused serious performance degradation and economic/safety problems in a variety of industrial and residential applications including aircraft, ships, wind turbines, dams, power transmission liens, heat pumps, refrigerators and air conditioners. Recent studies have reported that oil-infused superhydrophobic (Oil-SHPo) surfaces have excellent anti-icing ability due to its high droplet mobility, but few studies have clearly demonstrated detailed mechanisms of freezing delay on the surfaces. Here, we apply the Oil-SHPo wettability on commercially available Al surfaces and investigate how such wetting property effectively suppresses ice spreading under condensation frosting condition. Observed in a microscope test setup, microscale icing behaviors on the surfaces exhibit that its high droplet mobility makes droplet distribution with small mass diffusion rate between frozen drops and liquid drops, it leads to low ice propagation velocity. In particular, it is shown that infused oil viscosity plays a critical role in condensation growth rate and small viscosity is more desirable for icephobic surfaces. Heat exchangers with the Oil-SHPo wettability exhibit high droplet removal rate thanks to the influence of its extremely low contact angle hysteresis and it leads to the best anti-icing ability when compare to other test surfaces.
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서동현(Seo Donghyun),천성열(Cheun Seungyul),이승호(Lee Seungho) 한국지반환경공학회 2009 한국지반환경공학회논문집 Vol.10 No.6
본 연구에서는 상부 토피고가 낮거나 지반조건이 불량한 터널의 경우 기존 터널의 보강공법과 다른 선지보네일 보강공법을 적용한 터널의 설계 및 시공사례를 조사하였다. 신기술?신공법인 선지보네일 보강공법을 대단면 터널 상부지반에 보강하여 기존 터널 보강공법들에 비하여 보강효과 및 안정성 측면의 실효성을 확인하였다. 선지보네일 공법에 대한 설계, 현장시공 사례 및 계측 데이타를 조사하여 그 보강 결과를 확인하였으며, 터널 상부지반 선지보네일 보강에 따른 대단면 터널의 아칭 특성에 대하여 유한요소 수치해석 프로그램인 MIDAS/GTS를 이용하여 연구하였다. 이와 더불어 터널 상부지반에 선지보네일 공법을 적용함에 있어서 적절한 설치간격과, 적용시 공법의 보강효과를 극대화하기 위한 방법을 제시하였다. In this study, it was studied on arching characteristics of a grand section tunnel with pre-steel-rib nail reinforcement. In this study, we examine the adaptation of tunnel plan and the case which is based on the strengthening method for preexistence tunnel and other pre-steel-rib nail while the upper part of cover depth is low or soil condition is bad. When the pre-steel-rib nail as new technology and method reinforces the foundation placed of grand section tunnel, it is much better in strengthening effect, safety and effectiveness than the conventional one. After investigation about the plan pre-steel-rib nail method, construction case and calibration data, it was confirmed and examined about the upper part of tunnel for strengthening the pre-steel-rib nail thereby arching characteristics of grand section tunnel using MIDAS/GTS finite element program. Moreover we present the method that could upgrade the accurate installation interval and adaptation method for strengthening effect to adapt the pre-steel-rib nail method in a foundation placed over a tunnel.
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