• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.648-652
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• 2016

The study of $CO_2$ absorption in a packed column by 1,1,3,3-tetramethylguanidine (TMG) dissolved in ethylene glycol is presented. Absorption column of inner diameter 1 in and 0.6 m length was filled with Protruded-packing $0.16in{\times}0.16in$. We investigated the effect of operating conditions on overall mass transfer coefficients as well as on $CO_2$ removal efficiency. The loading values reached at about $1.0mol_{CO2}/mol_{TMG}$. In case of absorbent with lean $CO_2$ loading, the overall mass transfer coefficient was proportional to the concentration of TMG. However, in the range of more than ${\alpha}=0.5molCO_2/molTMG$, the overall mass transfer coefficients decreased with the concentration of TMG. It is due to the increasing of mass transfer resistance in liquid phase as increasing of viscosity at higher loading values.

• Solar Energy
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• v.13 no.2_3
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• pp.120-132
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• 1993

The purpose of this research is to study the characteristics of heat transfer in composite rotary heat pipe as modeled turbine rotating by a finite element analysis and experiment. Nu number, Re number, Pr number and dimensionless condensate layer thickness by thermal input and revolutions per minute were given as analysis factors. The comparison between calculated and experimental data showed similar tendency. Therefore the analysis method may be useful to predict the performance of composite heat pipe. The resistance on heat pipe showed the best effect of heat transfer by film condensation, by decreasing film condensation, the heat transfer rate from condenser was increased rapidly. The dimensionless condensate layer thickness according to Re number at given Pr number showed constant values, the dimensionless condensate layer thickness is proportionate to the square root of inverse of revolution number per minute. In this study Nu=A$({\delta}({\omega}/v)^{-1/2}Re^B)$ is used to the convection heat transfer coefficient and A=0.963, B=0.5025 were obtained as analysis predicts.

• 연구논문집
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• s.28
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• pp.137-143
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• 1998

In the case of a boiler, scale is made in the tube by the chemical reactions of Ca and Mg ions contained in the water, and heat transfer rate is reduced because of increasement of heat resistance in the pipe of the heat flow. Thus it brings to reduce the energy efficiency and to make environmental pollution by the use of chemicals for the prevention and removement of scale. In this paper, we discussed the design of electronic generator for dual ultrasonic transmitters and analyzed the effect of scale prevention by ultrasound.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.42.1-42.1
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• 2010

결정질 실리콘 태양전지의 전면 전극은 전극 면적으로 인한 손실(shading loss)를 줄이고 단락전류밀도(Jsc)를 높이기 위해 전극 너비를 줄이는 노력을 하고 있다. 하지만 전극 소성(firing) 시 전면 전극의 핑거(finger)와 버스바(busbar)의 너비 차이로 인해 전극 침투(fire-through) 정도가 달라질 수 있다. 본 연구에서는 전극 소성 공정 시 전면 전극의 너비에 따른 전극 침투 정도를 조사하기 위해 접촉 저항(specific contact resistance)과 재결정화(Ag recrystallite) 된 전면전극의 분포에 대해 비교하였다. 접촉 저항을 측정하기 위하여 transfer length method(TLM)를 이용하였다. 또한 전면 전극층을 제거한 후 실리콘 기판의 재결정 분포를 주사전자현미경(Scanning electron microscope : SEM)을 이용하여 관찰하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.189-205
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• 1996

The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.1
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• pp.28-38
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• 2014

The organic-inorganic composite membrane in polymer exchange membrane fuel cells (PEMFCs) have several fascinating technological advantages such as a proton conductivity, thermal stability and mechanical properties. As the inorganic filler, silicon carbide (SiC) fiber have been used in various fields due to its unique properties such as thermal stability, conductivity, and tensile strength. In this study, composite membrane was successfully fabricated by modified-silicon carbide fiber. Modified process, as a novel process in SiC, takes reaction by phosphoric acid after oxidation process (generated homogeniusly $SiO_2$ layer on SiC fiber). The mechanical property which was conducted by tensile test of the 5wt% modified-$SiO_2@SiCf$ composite membrane was better than that of Aquivion casting membrane as well as ion cxchange capacity(IEC) and proton conductivity. In addition, the single cell performance was observed that the 5wt% modified-$SiO_2@SiCf$ composite membrane was approximately $0.2A/cm^2$ higher than that of a Aquivion casting electrolyte membrane and electrochemical impedance was improved with the charge transfer resistance and membrane resistance.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.232-239
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• 2015

In this paper, we study the dry transfer technology utilizing PDMS (Polydimethylsiloxane) stamp of a large single-layer graphene grown on Cu-foil as catalytic metal by using Chemical Vapor Deposition (CVD). By changing the surface property of the target substrate through $UV/O_3$ treatment, we can transfer the graphene on the target substrate while minimizing mechanical damages of graphene layer. Multi-layer (1~4 layers) graphene was stacked on $SiO_2/Si$ wafer successfully by repeating thetransfer method/process and then optical transmittance and sheet resistance of graphene layers have been measured as a quality assessment.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.87-94
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• 2007

It has been argued that the use of plastics can cause problems during design and manufacture owing to their low strength, relatively poor thermal conductivity and large thermal expansion. However, the advantages of plastics e.g., corrosion resistance, low cost, curtailment of weight, design flexibility etc., can compensate abundantly for the disadvantages. This study analyzes and compares the heat transfer performance characteristics of automotive compact oil cooler composed of plastic tube bundle with conventional metal oil cooler on the same core area basis as diameter, tube thickness, number of tube or tube arrangement varies. The performance analyses are accomplished by use of computational fluid dynamics program Fluent 6.2, which is verified and compared with the results of performance tests. The result of analyses is coincided with that of experiments. Flow pattern at air side according to tube arrangement is dominant factor which affects heat dissipation in case of similar total heat transfer surface area.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.203-208
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• 2008

The purpose of this study is to compare the different shapes of condenser of the direct contact heat transfer from the heat pipe condenser to the receiving water using CFD. The heat transfer from the working fluid of the heat pipe to receiving fluid flows through the manifolder is one of the important part in evacuated solar collector system. The retrenchment of the thermal resistance between the heat pipe and the manifolder could increase the thermal performances of the whole system. Recently, direct heat transfer from the heat pipe condenser wall to the receiving water was suggested and accompanied experiments were achieved. This experiment shows the better performances of the direct contact heat transfer analogically. Preceding calculations are carried out for the performance comparison: mesh dependence test, discretization method test and equation model test. with these preceding tests, 4 different shapes of condenser are compared and each case were set up for the same heat flux at the condenser wall. The calculation result shows that the efficiency of the extended surface condenser shape is 10% higher then the that of the others.

• Nuclear Engineering and Technology
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• v.28 no.2
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• pp.175-184
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• 1996

A nuclide transfer by utilizing mass transfer coefficient and barrier response function defined for each barrier is proposed, by which the final nuclide transfer rate into the sea water can be evaluated. When simple and immediate quantification of the nuclide release is necessary in the conservative aspect, using this kind of approach may be advantageous since each layered barrier can be treated separately from other media in series in the repository system, making it possible to apply separate solutions in succession to other various media. Although one disadvantage is that while flux continuity can be maintained at the interface by using the exit nuclide flux from the first medium as the source flux for the next one, there may be no guarantee for concentration continuity, this problem could be eliminated assuming that there is no boundary resistance to mass transfer across the interface. Mass transfer coefficient can be determined by the assumption that the nuclide concentration gradient at the interface between adjacent barriers remains constant and barrier response function is obtained from an analytical expression for nuclide flow rate out of each barrier in response to a unit impulse into the barrier multiplied by mass transfer coefficient. Total time-dependent nuclide transfer rate from the barrier can then be obtained by convoluting the response function for the barrier with a previously calculated set of time-varying input of nuclide flow rate for the previous barrier.