• Journal of Welding and Joining
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• 제23권6호
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• pp.93-98
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• 2005

The purpose of this study is to investigate the characteristics of pb-free $Zn-(3\~6)\%Al-(1\~6)\%Cu$ solder alloys for ultra high temperature(>573K) which applied to air craft, space satellite, automotive, oil, gas well exploration and data logging of geo-thermal wells. Melting range, solderability, electric resistivity, microstructure and mechanical properties were examined with solder alloys casted in Ar gas atmosphere. $Zn-4\%Al-(1\~3)\%Cu,\;Zn-5\%Al-(2\~4)\%Cu\;and\;Zn-6\%Al-(3\~5)\%Cu$ alloys satisfied the optimum melting range of 643 to 673k for ultra high temperature solder. A melting temperature increased with increasing Cu content, but decreased with increasing Al content. The spreadability was improved with increasing hi content. But the content of Cu had no effect on the spreadability. The electric resistivity was lowered with increasing Al and decreasing Cu content. In all Zn-Al-Cu solder alloys, primary dendritic $\varepsilon$ phase(Zn-Cu), dendritic $\eta$ phase(Zn-Cu-Al), $\alpha(Al-Zn)-\eta$ eutectic and eutectoid phase were observed. The addition of Al increased the volume fraction of eutectic and eutectoid phase and it decreased f phases. Also, the addition of Cu increased slightly the volume fraction of e, the eutectic and eutectoid phases. With increasing total content of Al and Cu, a hardness and a tensile strength were linearly increased, but anelongation was linearly decreased.

• 대한기계학회논문집B
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• 제39권2호
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• pp.135-146
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• 2015

본 논문은 대형 상용기관을 모사한 정적연소실에서 매립지 가스의 연소 특성에 대한 복수의 논문 중 네 번째로, 열 발생 특성과 가시화 결과를 관찰하여 토치 연소의 특징을 논의하였다. 분석 결과 토치 연소는 주 연소실에 형성된 화염 면을 토치에서 분출되는 가스가 가속시킴으로 연소를 촉진한다. 이때 오리피스 직경이 4mm일 때는 토치에서 고온의 가스가 분출되며, 6mm 이상에서는 토치에서 형성된 화염이 직접 오리피스를 통과한다. 또한 메탄 분율, 토치 체적 그리고 오리피스 크기가 상호 연관적으로 작용하여 다양한 연소 형태를 야기하고 이에 따라 토치 연소의 효과가 매우 다르게 나타난다. 마지막으로 실물기관에서 연소 과정의 일관성을 보장하는 적절한 토치의 조건은 6mm 이상의 오리피스 직경과 0.15 이하의 오리피스 면적비를 동시에 만족시키는 것이다.

• 설비공학논문집
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• 제7권1호
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• pp.120-131
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• 1995

Thermodynamic analysis of extraction process from the constant pressure LNG(Liquefied Natural Gas) vessel was performed in this study. LNG was assumed as a binary mixture of 90% methane and 10% ethane by mole fraction. The thermodynamic properties such as temperature, composition, specific volume and the amount of cold energy were predicted during extraction process. Pressure as a parameter ranges from 101.3kPa to 2000kPa. The result shows the peculiar phenomena for the LNG as a mixture. Both vapor and liquid extraction processes were investigated by a computer model. The property changes are negligible in the liquid extraction process. For the vapor extraction process, the temperature in the vessel increases rapidly and the extracted composition of methane decreases rapidly near the end of extracting process. Specific volume of vapor has the maximum and that of liquid has the minimum during the process. When pressure is increased, specific volume of vapor decreases and that of liquid increases. It was found that specific volume of vapor phase had a major effect on the heat absorption at constant pressure during vapor extraction process. If the pressure of the vessel increases, the total cold energy which can be utilized from LNG decreased.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.652-657
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• 2007

This paper is an interim report on the investigation of thermodynamic properties of $CO_2$/oil mixture refrigerant. First, liquid density of POE (poly-ol ester) and PAG (poly alkylene glycol) were measured and expressed as a function of temperature. Then, a solubility equation was developed which enables us to calculate the weight fraction of $CO_2$ for the mixture in a liquid state. An experimental apparatus with a cell was constructed to measure P-$\upsilon$-T-$\chi$ data for $CO_2$/oil mixture. The volume of the cell was determined using a certain formula considering change in volume as a function of temperature and pressure. Then, experimental data were obtained over the temperatures $40^{\circ}C$, $50^{\circ}C$, $60^{\circ}C$, $70^{\circ}C$ and $80^{\circ}C$ with various mole fractions. Finally, assuming a primitive model of ideal gas, the volume of $CO_2$/oil mixture was predicted with a relatively larger error of 5.05% for $CO_2$/PAG and 8.81% for $CO_2$/POE. The volume of $CO_2$/oil mixtures would be better predicted using an appropriate equation of state, of which results will be reported soon.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.335-338
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• 2003

A finite element-based, integrated process model has been developed and applied to predict the detailed, three-dimensional aspects of the thermo-mechanical behavior occurring in the slab caster considering inclusion removal from molten steel by argon bubble flotation. Gas bubbles are simulated using the dispersion model calculating the volume fraction, and the bubble capture effect is included by a source term in the transport equation for particles. The process model is applied to the investigation of the effect of various process parameters on the inclusion removal in the molten steel.

• 설비공학논문집
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• 제5권4호
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• pp.249-256
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• 1993

Numerical method is applied to predict the time variation behavior of flammable mixture formation in a two dimensional enclosure from the beginning of gas leak. Additionally experimental method is used to consider qualitative aspects. Characteristics of flammable mixture formation such as distribution of flow and fuel mass fraction at various locations in the enclosure are determined for the following parameters: the various locations of leak at the bottom and aspect ratio of the enclosure. In the case of gas leak with small leak velocity from the bottom of enclosure gravitational force affects the formation of flammable mixture. Aspect ratio of the enclosure also affects the formation of flammable mixture. The volume of the region of recirculating flow is dominant factor affecting the formation mixture.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.49-54
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• 1998

The growth of diamond films in plasma enhanced chemical vapor deposition(PECVD) processes requires high substrate temperatures and gas pressures, as well as high-power excitation of the gas source. Thus determining the substrate temperature in this severe environment is a challenge. The issue is a critical one since substrate temperature is a key parameter for understanding and optimizing diamond film growth. The precise Si substrate temperature calibration based on rapid-scanning spectroscopic ellipsometry have been developed and utilized. Using the true temperature of the top 200 ${\AA}$ of the Si substrate under diamond growth conditions, real time spectroellipsometry (RTSE) has been performed during the nucleation and growth of nanocrystallind thin films prepared by PECVD. RTSE shows that a significant volume fraction of nondiamond(or{{{{ {sp }^{2 } -bonded}}}}) carbon forms during thin film coalescence and is trapped near the substrate interface between ∼300 ${\AA}$ diamond nuclei.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.594-596
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• 2007

Using an oedometer cell instrumented to measure the evolution of electromagnetic properties, small strain stiffness, and temperature, we conducted consolidation tests on four types of sediments. The tested specimens include sediments with different gas hydrate saturation at four stages of loading. The test results show that the electromagnetic and mechanical properties of hydrate-bearing marine sediments are governed by the vertical effective stress, stress history, porosity, hydrate saturation, fabric, ionic concentration of the pore fluid, and temperature. The results also show that permittivity and electrical conductivity data can be combined to estimate hydrate volume fraction in laboratory sediments, methodology that might eventually be extended for estimation of hydrate concentrations in field settings.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.291-293
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• 2011

In this paper, the problem of transonic aerodynamic characteristics of a NACA0012 airfoil is numerically investigated in the inviscid gas-droplet two-phase flow with the compressible two-fluid model. In the present study, the airfoil flight in the cloud is simulated by taking account of the viscous drag of the droplets, the heat transfer, the phase change, and the droplet fragmentation The two-fluid equation system is solved by the fractional-step method and the WAF-HIL scheme. The effects of size and volume fraction of the droplets on the flow characteristics of the airfoil in the cloud are elaborated and discussed.

• 한국전산유체공학회지
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• 제10권2호
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• pp.21-29
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• 2005

In this paper, we present the theoretical and numerical results of scavenge characteristics in a small subchamber of an HCCI(Homogeneous Charge Compression Ignition) engine. Two theoretical models are proposed in prediction of the scavenge time and the efficiency; one is the non-mixing model in which the input gas(CH4) and the existing gas(air) do not mix at all, and the other is the fully-mixed model in which the two gases are assumed to mix completely before ejection. Focus is also given to the effect on the scavenge performance of the size of the chamber outlet.