• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.208-214
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• 2008

The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids (the Lennard-Jones fluid, water and aqueous sodium-chloride solution) confined between two plates that are separated by 1.086 nm; included in the equilibrium properties are the density distribution and the static structure, and the diffusivity in the dynamic property. Three kinds of fluids considered in this study are. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.208-214
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• 2008

The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids (the Lennard-Jones fluid, water and aqueous sodium-chloride solution) confined between two plates that are separated by 1.086 nm; included in the equilibrium properties are the density distribution and the static structure, and the diffusivity in the dynamic property. Three kinds of fluids considered in this study are. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.

• 한국전산유체공학회지
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• 제14권1호
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• pp.24-34
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• 2009

The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids confined between two plates that are separated by 1.086 nm; included in the statical properties are the density distribution and the static structure, and the autocorrelation velocity function in the dynamic property. Three kinds of fluids considered in this study are the Lennard-Jones fluid, water and aqueous sodium-chloride solution. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1266-1274
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• 2006

A numerical study is performed to investigate the effect of inner surface roughness and micro-particles on adiabatic single phase frictional pressure drop in a perfect square micro channel. With the variation of particles sizes (0.1 to $1{\mu}m$) and occupied volume ratio (0.01 to 10%) by particles, the Eulerian multi-phase model is applied to a $100{\mu}m$ hydraulic diameter perfect square micro channel in laminar flow region. Frictional pressure loss is affected significantly by particle size than occupied volume ratio by particles. The particle properties like density and coefficient of restitution are investigated with various particle materials and the density of particle is found as an influential factor. Roughness effect on pressure drop in the micro channel is investigated with the consideration of roughness height, pitch, and distribution. Additionally, the combination effect by particles and surface roughness are simulated. The pressure loss in microchannel with 2.5% relative roughness surface can be increased more than 20% by the addition of $0.5{\mu}m$ diameter particles.

• Advances in nano research
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• 제15권3호
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• pp.191-201
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• 2023

In order to develop better method to enhance and control the flow and heat transfer inside the radiator of electronic device, the synergistic effect of MHD nanofluids and porous medium on the flow and heat transfer in rectangular opened channel is simulated using Lattice Boltzmann method. Three nanofluids of CuO-water, Al₂O₃-water and Fe₃O₄-water are studied to analyze the influence of the type of nanofluid on the synergistic effect. The simulation results show that the porous medium can increase the flow velocity in fluid zone adjacent to the porous medium and enhance the heat transfer on the surface of the channel. Under no magnetic field, when the porosity of porous medium is 0.8, the Nusselt number is 4.46% higher than when the porosity is 0.9. Al₂O₃-water has the best heat transfer effect among the three nanofluids. At Ф=0.06, Ha=100, θ=90°, ε=0.9, Nu of Al₂O₃-water is 6.51% larger than that of CuO-water and 5.05% larger than that of Fe₃O₄-water. Magnetic field enhances seepage in porous medium and inhibits heat transfer in the bottom wall. When Ha=30 and 60, the inhibiting effect is the most significant as the magnetic field angle is 90°. And when Ha=100, the inhibiting effect is the most significant as the magnetic field angle is 120°.

• 한국생산제조학회지
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• 제25권6호
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• pp.410-420
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• 2016

The geometric dimension and shape of microchannels that are formed during surface texturing are widely studied for applications in flow control, and drag and friction reduction. In this research, a new method for controlling the deformation of U channels during micro-rolling-based surface texturing was developed. Since the width of the U channels is almost constant, controlling the depth is essential. A calibration procedure of initial rolling gap, and proportional-integral PI controllers and a linear interpolation have been applied simultaneously to control the depth. The PI controllers drive the position of the pre-U grooved roll as well as the rolling gap. The relationship between the channel depth and rolling gap is linearized to create a feedback signal in the depth control system. The depth of micro channels is studied on A2021 aluminum lamina surfaces. Overall, the experimental results demonstrated the feasibility of the method for controlling the depth of microchannels.

• 대한기계학회논문집B
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• 제41권6호
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• pp.429-434
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• 2017

분자-연속체 하이브리드 기법은 연속체 유체역학으로 예측하기 어려운 마이크로/나노 스케일 유동에 대해 개발되고 발전해 왔다. 분자동역학은 고체표면 주변 영역에서 사용되고, 나머지 영역에서는 나비아스톡스 방정식이 사용된다. 본 연구에서는 나노채널에서 고체-액체 상호작용과 표면 거칠기의 영향을 연구하기 위해 분자-연속체 하이브리드 기법을 이용하여 쿠에트 유동을 해석하였다. 우리는 고체-액체 상호작용 힘인 표면 에너지와 표면 거칠기가 유동의 표면 경계조건에 영향을 주는 것을 발견하였다. 표면 에너지가 낮을 때에는 유동이 고체 표면에서 미끄러짐이 발생하였고, 표면 에너지가 증가함에 따라 미끄러짐의 크기가 감소하였다. 표면 에너지가 높을 때에는 로킹(locking) 경계조건이 형성되었다. 또한 표면 거칠기는 유동이 고체 표면에서 미끄러지는 것을 방해하여 로킹 경계조건이 잘 형성되도록 영향을 주었다.

• 설비공학논문집
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• 제23권6호
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• pp.449-469
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• 2011

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering during 2010. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of general thermal and fluid flow, fluid machinery, and new and renewable energy. Various topics were presented in the field of general thermal and fluid flow. Research issues mainly focused on the thermal reliability of axial fan and compressor in the field of fluid machinery. Studies on the design of ground source heat pump systems and solar chemical reactors were executed in the field of new and renewable energy. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (3) Refrigeration systems with alternative refrigerants such as hydrocarbons, mixed refrigerants, and CO2 were studied. Performance improvement of refrigeration systems are tried applying various ideas of refrigerant subcooling, dual evaporator with hot gas bypass control and feedforward control. The hybrid solar systems combining the solar collection devices with absorption chillers or compression heat pumps are simulated and studied experimentally as well to improve the understanding and the feasibility for actual applications. (4) Research trend in the field of mechanical building facilities has been found to be mainly focused on field applications rather than performance improvements. Various studies on heating and cooling systems, HVAC facilities, indoor air environments and energy resources were carried to improve the maintenance and management of building service equipments. In the field of heating and cooling systems, papers on a transformer cooling system, a combined heat and power, a slab thermal storage and a heat pump were reported. In the field of HVAC facilities, papers on a cooling load, an ondol and a drying were presented. Also, studies on HVAC systems using unutilized indoor air environments and energy resources such as air curtains, bioviolence, cleanrooms, ventilation, district heating, landfill gas were studied. (5) In the field of architectural environment and energy, studies of various purposes were conducted such as indoor environment, building energy, renewable energy and green building. In particular, renewable energy and building energy-related researches have mainly been studied reflecting the global interest. In addition, many researches which related the domestic green building certification of school building were performed to improve the indoor environment of school.

• Korean Chemical Engineering Research
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• 제57권5호
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• pp.730-734
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• 2019

열영동은 매질의 온도 구배에 의해 입자가 이동하는 현상이다. 본 논문에서는 미세유체 채널에서 입자의 열영동 현상에 대해서 논의한다. 흐름이 없는 비유동 채널에서 열원인 백금 와이어에 가해지는 전압에 비례해서 열영동에 의한 마이크로 입자의 이동이 더 크게 나타남을 확인하였다. 전압에 따른 백금 와이어 주변 온도 변화는 Callendar-van Dusen 식을 이용하여 예측하였다. 동일한 시스템에서 나노 입자의 열영동 현상을 관찰한 결과, 나노 입자도 마이크로 입자와 유사한 열영동 거동을 보임을 확인하였다. 마지막으로 Y 모양 미세유체 채널을 제작하고 백금 와이어 열원을 채널 내에 설치하여, 채널을 흐르는 현탁액 내의 입자의 열영동 현상을 구현하고, 이를 기반으로 현탁액의 흐름을 제어할 수 있음을 보인다.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.716-727
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• 2005

Comprehensive measurements for velocity and temperature fields have been conducted. A Micro PIV 2-color LIF system have been setup to measure the buoyancy driven fields in a 1-mm heated channel with low Grashof-Prandtl numbers [$86]. Fluorescence microscopy is combined with an MPIV system to obtain enough intensity images and clear pictures from nano-scale fluorescence particles. The spatial resolution of the Micro PIV system is $75{\mu}m\;by\;67{\mu}m$ and error due to Brownian motion is estimated $1.05\%$. Temperature measurements have achieved the $4.7\;{\mu}m$ spatial resolution with relatively large data uncertainties the present experiment. The measurement uncertainties have been decreased down to less than ${\pm}1.0^{\circ}C$ when measurement resolution is equivalent to $76\;{\mu}m$. Measured velocity and temperature fields will be compared with numerical results to examine the feasibility of development as a diagnostic technique.