분자동역학 전산모사를 이용한 박막의 불안정성 및 나노 구조물 형성에 관한 연구

한민섭(Minsub Han),이준식(Joon Sik Lee),박승호(Seungho Park),최영기(Young Ki Choi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

It has recently been shown that the instability of thin film of a nanoscale can be used in the processes of<br/> building nano-size structures, which have potential practical importance in nanotechnology. Molecular<br/> dynamics simulation is conducted to probe the thin fluid film of a nano-size and its dynamic behavior during<br/> destabilization and structure formation. Non-continuum characteristics are shown in the properties like<br/> pressure tensor, viscosity, and thermal conductivity. The thermocapillary force induces a slow growth of long<br/> waves in the scale considered. A long-range interaction with the solid wall induces vertical structures, whose<br/> formation time and space between neighbors are proportional to the strength of the interaction.

다상 유체 시스템의 다중 스케일 시뮬레이션 기법에 관한 연구

한민섭(Minsub Han) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.6

다상 유체 시스템에 적용할 수 있는 다중스케일 입자 시뮬레이션 기법을 개발하였다. 거시 모델과 미시모델이 만나는 경계영역에서 세가지로 구별되는 기능을 수행하도록 하였다. 먼저, 기상과 액상을 분리하여 연결하기 위해 벽을 설정하였다. 또 경계영역을 근처에서 경계의 위치를 측정하고 이것에 벽의 각도와 위치가 연동하여 접촉각 값을 미시모델에서 거시모델로 전달하게 하였다. 마지막으로, 입자의 삽입과 제거를 통해 경계영역의 질량과 온도를 거시적 조건에 맞추도록 하였다. 이 알고리즘들을 적용한 완전습윤과 부분습윤 시스템들은 좋은 결합 결과를 보였다. A multiscale particle simulation technique that can be applied to a multiphase fluid system has been developed. In the boundary region where the macroscopic- and microscopic-scale models overlap each other, three distinctive features are introduced in the simulation. First, a wall is set up between the gas and liquid phases to separate them and match the phases respectively to the macroscopic conditions stably. Secondly, the interfacial profile is obtained near the matching region and the wall translates and rotates to accommodate the change in the liquid-vapor interfacial position in the molecular model. The contact angle thus obtained can be sent to the macroscopic model. Finally, a state of mass and temperature in the region is maintained by inserting and deleting the particles. Good matching results are observed in the cases of the complete and partial wetting fluid systems.

고체 면에 흡착된 박막에서의 분리압력 특성에 관한 연구

한민섭(Minsub Han) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.2

The disjoining pressure is an important physical property in modeling the small-scale transport phenomena on thin film. It is a very useful definition in characterizing the non-continuum effects that are not negligible in heat and mass transport of the film thinner than submicro-scales. We present the calculated values of disjoining pressure of He, Kr and Xe thin films absorbed on graphite substrate using Molecular Dynamics Simulation (MD). The disjoining pressure is accurately calculated in the resolution of a molecular scale of the film thickness. The characteristics of the pressure are discussed regarding the molecular nature of the fluid system such as molecular diameter and intermolecular interaction parameters. The MD results are also compared with those based on the continuum approximation of the slab-like density profile and the results on other novel gases in the previous study. The discrepancies of the continuum model with MD results are shown in all three configurations and discussed in the view point of molecular features.

계면 열전달 특성에 대한 분자동력학 시뮬레이션 연구

한민섭(Minsub Han) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.4

나노스케일 액체브릿지의 기계적, 열적 특성에 관한 분자시뮬레이션 연구

한민섭(Minsub Han),이준식(Joon Sik Lee),박승호(Seungho Park),권오명(Ohmyoung Kwon) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

The micro- and nano-scale devices and probes are recently the area of intense research. Many of them operate mechanically in an ambient condition and involve the liquid bridge or capillary force in their function. The mechanical and thermal properties of the nanoscale liquid bridge are investigated using the molecular simulation. The non-equilibrium molecular dynamics simulation (NEMD) and grand canonical molecular dynamics simulation (GCMD) are performed simulating the ambient state of constant volume or humidity. Argon liquid bridge is formed between molecularly-flat surfaces of Pt atoms and its static and dynamics states are studied. First, the adsorption property of the liquid bridge is considered. The capillary force induced by the bridge is also characterized. The discrepancy with the previous studies in literature is discussed.

분자동력학 시뮬레이션을 이용한 나노채널 대류에서의 열류 분포에 대한 연구

한민섭(Minsub Han),이준식(Joon Sik Lee),박승호(Seungho Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

We study the convective heat transport phenomenon of liquid in a nanoscale straight channel by performing the nonequilibrium molecular dynamics simulation (NEMD). Fundamental heat transfer phenomenon distinctive in a nanoscale is reported by Han and Lee [Phys. Rev. E 70, 061205 (2004)]. It is the significant heat transfer in the upstream direction even in the absence of temperature gradient in the direction. A planar Poiseuille flow is considered in the simulation, where liquid argon in a straight channel of Pt atoms is driven by a gravity-like body force with periodic boundary conditions applied in the tangential directions to the surfaces. The heat transfer is induced by the active role of intermolecular force and plane peculiar velocity. It becomes significant when the velocity gradient is sizable in the range of the intermolecular force. The generalized Fourier's law in the literature is compared with NEMD results.

고체 위의 박막에서의 분리압력 및 안정 특성에 관한 연구

한민섭(Minsub Han) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

The disjoining pressure is critical in modeling the transport phenomena in small scales. They are very useful in characterizing the non-continuum effects that are not negligible in heat and mass transports in the film of less than submicro-scales. We present the disjoining pressure of thin film absorbed on solid substrate using Molecular Dynamics Simulation (MD). The disjoining pressure with respect to the film thickness is accurately calculated in the resolution of a molecular scale. The characteristics of the pressure are discussed regarding the molecular nature of the fluid system like molecular diameter and intermolecular interaction. Also, the MD results are compared with those based on the macroscopic approximation of the slab-like density profile. Significant discrepancy is observed when the effective film thickness is less than several molecular diameters.

단면형상 변화에 따른 전열교환기 열전달 특성변화에 대한 연구

김응복(Eung-Bok Kim),한민섭(Minsub Han),김내현(Nae-Hyun Kim),원태연(Tae-Yeon Won) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.5

It is a critical task to keep the ventilation system working in a proper and efficient manner in large multi-storey buildings, and the enthalpy exchanger is becoming an increasingly important part of the ventilation system by playing the function of channeling heat and moisture. We present a computational study on the heat transfer performance of the cross-flow enthalpy exchanger, which is in large use for residential buildings. The ducts are considered whose crosssectional shapes resemble triangle and longitudinal centerline a cosine wave. It is shown that, as the cross-sectional shape departs from triangle, the heat transfer performance of the duct tends to deteriorate. Also, applying the wave-like shape to the longitudinal centerline of the duct increases the rate of heat transfer and the applied pressure-gradient at the same time. The origin of the performance variations in the cases considered are quantitatively analyzed and discussed.

근적외선 가열 시스템의 냉각 성능에 대한 수치적인 연구

유근표(Keun-Pyo Yoo),한민섭(Minsub Han),김제덕(Jae-Duck Kim),최원택(Won-Taek Choi) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.5

A near infrared (NIR) heating system has advantages over the conventional convection-based systems, in terms of heating uniformity and energy efficiency. When it is over-heated during its operation, the radiation lamp gets blackened, and the life of the radiation module becomes severely limited. The heat transfer system in the module is based on a high operating-temperature, and the radiation makes it difficult to analyze in detail the reliability issue, with an experimental approach alone. We developed a numerical heat-transfer model of the NIR heating system. We applied a ray-tracing method on the radiative heat transport, and a finite volume method on the conductive and convective systems, respectively. The cooling performance of the system is presented, based on the energy and flow distributions in the module. The factors that directly affect the module life are analyzed, such as the surface temperatures of the lamp glass and the reflector, and design improvements are discussed.

태양전지 시스템을 위한 고정 집광기의 광학 설계에 관한 연구

하성문(Seong moon Ha),한민섭(Minsub Han),이준식(Joon sik Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

The Concentrated Photovoltaic system (CPV) has advantage over the non-concentrated one in that they can generate more electricity per cell and thus reduce the overall energy price. However, the system is not suitable for the installments in individual house, small building, or remote places because it normally needs an active tracking component that requires frequent maintenance. The Static Concentrated Photovoltaic system (SCPV) is aimed at concentrating sunlight onto PV in a static position without active tracking component. The majority of the studies on SCPV are based on either non-imaging reflection or total internal reflection, and the resulting concentration ratio (CR) remains low. The purpose of our study is to improve CR of SCPV by designing novel focusing lens based on non-imaging lens. The static concentrator is composed of the Fresnel lenses, in which the size and angle of each prism unit is optimized by tracking a large number of ray paths computationally and assessing the global performance for various designs. A better performance in terms of CR and exergy than previously reported in literature is obtained.