• 한국자기학회:학술대회 개요집
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• 한국자기학회 2015년도 임시총회 및 하계학술연구발표회
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• pp.15-16
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• 2015

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2005년도 하계학술연구발표회 논문개요집
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• pp.58-59
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• 2005

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 추계학술발표회요약집
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• pp.187.1-187
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• 1999

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2267-2272
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• 2007

The present study investigates the two dimensional flow and heat/mass transfer characteristics of wavy duct with various corrugation angles. For the heat/mass transfer coefficients, a naphthalene sublimation technique is used. Numerical analysis and wall pressure measurement show detailed two dimensional flow features. The corrugation angles change from 145$^{\circ}$ to 100$^{\circ}$. The operating Reynolds numbers based on the duct hydraulic diameter vary from 700 to 3,000. The duct aspect ratio maintains 7.3. On the pressure wall, strong flow mixing enhances heat/mass transfer coefficients at the front position. In addition, the rear side of pressure wall, the near of peak, is affected by the acceleration and the shedding of main flow. On the suction wall, however, flow separation and reattachment lead to the valley and the peak of heat/mass transfer coefficient. Also, highly increasing boundary layer at the suction wall affects the decrease of heat/masst transfer. As decreasing corrugation angles, the spanwise average Sherwood number increases and the peak or the valley positions of the local Sherwood number are varied.

• 설비공학논문집
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• 제8권4호
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• pp.537-549
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• 1996

A numerical study of heat and mass transfer has been carried out for a frost formation process on a circular cylinder in a cross flow including the effect of buoyancy. Studies include cases of low and high Reynolds number flows. The effect of normal velocity at the surface which is produced due to mass transfer was included in the analysis as well as heat transfer contribution generated due to mass transfer. Variations of heat transfer and frost growth both in time and in the circumferential direction have been obtained for various buoyancy parameters. The effect of flow directions(identical or opposite directions to the gravity) has been studied to yield different frost growth. Our results have been compared with existing experimental data and are in good agreement. Buoyancy analyses for a high Reynolds number flow agree with full numerical solutions for the case of having the same flow direction as gravity. However, for the opposite direction case, the boundary layer analyses would not be applicable to predict frost growth except the region near the stagnation point.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.36-41
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• 2001

In order to simulate wake of stator and a gas turbine engine's balde row, acryl cylinder and a linear turbine cascade were used respectively in this study. Experimental of heat transfer distributions was done on the passage endwall and blade suction surface. Temperature distributions on the experimental regions were obtained through image processing system by using the cholesteric type liquid crystal which has chain structure of metyl$(CH_3)$. To represent the degree of heat transfer, dimensionless St number was used. The results show that heat transfer on the blade suction surface was increased due to the wake from the cylinder and was decreased as the distance between cylinder row and blade row increases. Because of groth of passage vortex, heat transfer distributions on the trailing edge area showed triangular shape which was little changed with wake. On the other hand, heat transfer on the passage endwall was decreased due to the wake from cylinder. As the distance between cylinder row and blade row increases, heat transfer was more decreased.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.232.2-232.2
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• 2014

Since its discovery in 2004, graphene, a sp2-hybridized 2-Dimension carbon material, has drawn enormous attention. A variety of approaches have been attempted, such as epitaxial growth from silicon carbide, chemical reduction of graphene oxide and CVD. Among these approaches, the CVD process takes great attention due to its guarantee of high quality and large scale with high yield on various transition metals. After synthesis of graphene on metal substrate, the subsequent transfer process is needed to transfer graphene onto various target substrates, such as bubbling transfer, renewable epoxy transfer and wet etching transfer. However, those transfer processes are hard to control and inevitably induce defects to graphene film. Especially for wet etching transfer, the metal substrate is totally etched away, which is horrendous resources wasting, time consuming, and unsuitable for industry production. Thus, our group develops one-step process to directly grow graphene on glass substrate in plasma enhanced chemical vapor deposition (PECVD). Copper foil is used as catalyst to enhance the growth of graphene, as well as a temperature shield to provide relatively low temperature to glass substrate. The effect of growth time is reported that longer growth time will provide lower sheet resistance and higher VSG flakes. The VSG with conductivity of $800{\Omega}/sq$ and thickness of 270 nm grown on glass substrate can be obtained under 12 min growing time. The morphology is clearly showed by SEM image and Raman spectra that VSG film is composed of base layer of amorphous carbon and vertically arranged graphene flakes.

• 설비공학논문집
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• 제15권10호
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• pp.809-820
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• 2003

The present study investigates effects of flow velocity on the convective heat/mass transfer characteristics in wavy ducts of a primary surface heat exchanger application. Local heat/mass transfer coefficients on the wavy duct sidewall are determined by using a naphthalene sublimation technique. The flow visualization technique is used to understand the overall flow structures inside the duct. The aspect ratio and corrugation angle of the wavy duct is fixed at 7.3 and 145$^{\circ}$ respectively, and the Reynolds numbers, based on the duct hydraulic diameter, vary from 100 to 5,000. The results show that there exist complex secondary flows and transfer processes resulting in non-uniform distributions of the heat/mass transfer coefficients on the duct side walls. At low Re (Re<1000), relatively high heat/mass transfer regions like cell shape appear on both pressure and suction side wall due to the secondary vortex flows called Taylor-Gortler vortices perpendicular to the main flow direction. However, at high Re (Re>1000), these secondary flow cells disappear and boundary layer type flow characteristics are observed on pressure side wall and high heat/mass transfer region by the flow reattachment appears on the suction side wall. The average heat/mass transfer coefficients are higher than those of the smooth circular duct due to the secondary flows inside wavy duct. And also friction factors are about two times greater than those of the smooth circular duct.

• KIEAE Journal
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• 제7권5호
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• pp.53-58
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• 2007

In order to predict the indoor air pollutant, the VOCs emission rate is used through small chamber in the design process. However, the small chamber method has limitations as the convective mass transfer coefficient, the most important factor when predicting VOCs contamination of indoor air, is different between the small chamber result and the measured data in the actual building. Furthermore, the existing studies which analyzed mass transfer coefficient in the small chamber were directed on the small chambers developed at the time and FLEC(Field and Laboratory Emission Cell), thus, are different from the current small chamber which has been changed with improvements. The purpose of this study is to determine the emission rate of pollutant in multi-layered building materials, and predict the indoor pollutant concentration through the CFD(Computational of Fluid Dynamics) and CRIAQ2 based on the mass transfer coefficient on singled-layered building material by using the current small chamber widely used in Korea. Futhermore, this study used the new convective mass transfer coefficient(hm') which indicates the existing convective mass transfer coefficient(hm) including VOC partition coefficient(k). Also, formaldehyde was selected as target pollutant.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.321-325
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• 2008

초음속 유동장내에 분사된 2차제트 주변에서의 열전달 현상을 고찰 하였다. 초음속 유동장내에 분사되는 2차유동의 Jet to freestream momentum ratio(운동량비)의 변화와, 2차유동 분사각도에 따른 2차 분사홀 주변의 열전달 특성을 파악하기 위하여 홀 주변의 표면온도 변화를 고속 적외선 카메라를 통하여 측정하였으며, 이를 이용하여 비정상 열유속 기법을 바탕으로 열유속을 계산하였다. 운동량비가 증가할 수록 열전달 현상이 강화 되었으며, $15^{\circ}$ 기울어진 분사보다는 수직 분사의 경우에 더 강한 열전달 현상이 발생되었다. 이를 통해 분사비와 분사 각도가 표면 열전달 분포에 중요한 요인으로 작용함을 확인할 수 있었다.