• 설비공학논문집
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• 제19권12호
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• pp.821-830
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• 2007

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction steam line- inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical results using the FLUENT code and the down scale experimental data on effect of geometry of the impingement baffle plate on the shell wall thinning. Additionally, a new type impingement baffle plate was installed above the impingement baffle plate in the feedwater heater and then the numerical and experimental study were performed in the same progress.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.9-16
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• 2007

Since the liquid phase LPG injection(LPLI) system has an advantage of higher power and lower emission characteristics than the mixer type fuel supply system, many studies and applications have been conducted. However, the heat extraction, due to the evaporation of liquid fuel, causes not only a dropping of LPG fuel but also icing phenomenon that is a frost of moisture in the air around the nozzle tip. Because both lead to a difficulty in the control of accurate air fuel ratio, it can result in poor engine performance and a large amount of HC emissions. The experimental investigation was carried out on the bench test rig in this study. It was found that n-butane, that has a relatively high boiling point($-0.5^{\circ}C$), was a main species of droplet composition and also found that the droplet problem was improved by the use of a large inner to outer bore ratio nozzle whose surface roughness is smooth. The icing phenomena were decreased when the an engine head temperature was increased, although a large amount of icing deposit was still observed in the case of $87^{\circ}C$. Also, it was observed that the icing phenomenon is improved by using anti-icing bushing.

• 한국분무공학회지
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• 제14권4호
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• pp.147-152
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• 2009

Since a liquid-phase LPG injection system allows accurate control of fuel injection and increase in volumetric efficiency, it has advantages in achieving higher engine power and lower emissions compared to the mixer type LPG supplying system. However, this system also leads to an unexpected event called icing phenomenon which occurs when moisture in the air near the injector freezes and becomes frost around the nozzle hole due to extraction of heat from surrounding caused by instant fuel vaporization. As a result, it becomes difficult to control air/fuel ratio in engine operation, inducing exacerbation of engine performance and HC emission. One effort to mitigate icing phenomenon is to attach anti-icing injection tip in the end of nozzle. Therefore, in this study, the effect of engine operation parameters as well as surrounding conditions on icing phenomenon was investigated in a bench test rig with commercially-used anti-icing injection tips. The test results show that considerable ice was deposited on the surface near the nozzle hole of the anti-icing tip in low rpm and low load operating conditions in ambient air condition. This is because acceleration of detachment of deposited ice from the tip surface was induced in high load, high rpm conditions, resulting in decrease in frost accumulation. The results of the bench testing also demonstrate that little or no ice was formed at surrounding temperature below a freezing point since the absolute amount of moisture contained in the intake air is too small in such a low temperature.

• 방사성폐기물학회지
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• 제16권2호
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• pp.165-172
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• 2018

용융염-액체금속 추출공정에서 형성되는 액적 크기를 추정하는 방안으로 용융염-액체금속 계를 상온에서 유사한 물-수은 계로 대체하여 액적 형성 실험을 노즐의 종류에 따라 수행하여 Scheele-Meister 모델의 적용성을 평가하였다. 실험에서 액적의 크기 측정은 디지털카메라와 이미지분석 소프트웨어를 사용하였으며 노즐은 0.018 cm과 0.025 cm의 구멍 크기를 가지며 수은의 통과 길이가 1.3 cm인 상용 니들과 두께가 0.5 cm이며 0.0148 cm 구멍 2개, 0.0135 cm 구멍 3개, 0.0135 cm 구멍 4개인 것을 제작하여 사용하였다. 각각의 노즐에서 형성된 액적은 노즐 아래 20 cm까지 안정적인 구형을 유지하였다. 액적 크기의 측정치를 Scheele-Meister 모델의 추정치와 비교하였을 때 10% 오차 범위 안에서 일치하였다. 실험 결과는 물-수은 계에서 액적을 안정적으로 형성시키는 노즐에 대해 액적 크기 추정을 위한 Scheele-Meister 모델이 적용될 수 있음을 보였다.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.714-721
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• 2016

유가금속이 혼합된 비철합금의 습식 제련의 용이성을 위해서, 주석과 황동 용탕으로부터 표면적이 넓은 평판형 응고체를 제조하는 공정을 제안하였다. 금속 용탕을 그라파이트 도가니의 노즐로부터 드롭렛(droplet) 형상으로 떨어뜨릴 수 있도록 STAR-CCM+ 프로그램을 이용하여 노즐의 직경을 0.5, 1.0, 2.0 mm로 변화시키며 시뮬레이션을 진행하였다. 주석과 황동 모두 0.5 mm 노즐에서는 융액이 흐르지 않았으며, 2.0 mm 에서는 연속적인 분사가 진행되었고, 1.0 mm에서는 목적한 드롭렛이 형성되었다. 시뮬레이션 결과를 바탕으로 목적한 드롭렛이 형성되는 1.0 mm 노즐을 이용하여 용융된 주석, 황동 용탕 드롭렛을 $40^{\circ}$의 경사를 가진 티타늄 충격판에 충돌시켜 표면적이 증가된 디스크형 응고체를 10분 내에 성공적으로 제조하였다. 평면 응고체의 무게, 평균두께, 표면적은 주석의 경우 각각 0.15 g, $107.8{\mu}m$, $3.71cm^2$ 이었으며, 황동의 경우 1.16 g, $129.15{\mu}m$, $23.98cm^2$로 확인되었다. 형성된 응고체의 표면적은 드롭렛에 대비하여 각각 8.2, 17.6배로 증가되었다. 제안된 공정을 이용하여 다른 유가금속 합금의 표면적 향상 공정에도 비용과 시간 절감이 기대되었다.

• 대한기계학회논문집B
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• 제31권1호
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• pp.1-7
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• 2007

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle - installed downstream of the high pressure turbine extraction steam line - inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical analysis results using the FLUENT code and the down scale experimental data in an effort to determine root causes of the shell wall thinning of the high pressure feedwater heaters. The numerical analysis and experimental data were also confirmed by actual wall thickness measured by an ultrasonic test.

• Fisheries and Aquatic Sciences
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• 제17권1호
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• pp.67-73
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• 2014

The oil in mackerel muscle was extracted using an environment friendly solvent, supercritical carbon dioxide (SC-$CO_2$) at a semibatch flow extraction process and an n-hexane. The SC-$CO_2$ was maintained at a temperature of $45^{\circ}C$ under pressures ranging from 15 to 25 MPa. The flow rate of $CO_2$ (27 g/min) was constant during the entire 2 h extraction period. The fatty acid composition of the oil was analyzed using gas chromatography (GC). Significant concentrations of eicosapentaenoic acid (EPA) acid and docosahexaenoic acid (DHA) acid were present in the SC-$CO_2$ extracted oil. The oil extracted using SC-$CO_2$ exhibited increased stability compared with n-haxane extracted oil. Particles of mackerel oil together with the biodegradable polymer, polyethylene glycol (PEG) were formed using a gas saturated solution process (PGSS) with SC-$CO_2$ in a thermostatted stirred vessel. Different temperatures ($45-55^{\circ}C$), pressures (15-25 MPa) and a nozzle size $400{\mu}m$ were used for PGSS with a 1 h reaction time. The stability of mackerel oil in the particles did not changed significantly.

• 소성∙가공
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• 제3권1호
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• pp.63-83
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• 1994

In this paper, the slab method have been applied to investigate the strip casting process in which hot coil is produced from molten steel directly. In the twin roll strip casting process, molten steel supplied by the nozzle cools and solidifies due to the heat extraction effect of the rolls and hot rolling of the solidified shell takes place simultaneously. The analysis of hot rolling has been carried out by using the existing results of solidification analysis for the twin roll strip casting process. The current slab method provides basic design data such as roll separation force, rolling torque, rolling power as well as end dam separation force which are required to design strip caster. The effect of friction on the basic process parameters are investigated also. It is shown that the use of appropriate friction coefficient is important and that the characteristics of hot rolling in the twin-roll strip casting process is quite different from the conventional hot rolling processes.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.45-48
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• 2007

기존에 사용되는 피에조 타입의 센서는 추력의 측정 범위가 제한되어 있으므로 이를 개선하고자 레이져 변위측정기와 cantilever를 이용하여 변위 측정 장치를 개선하였고, 스테인레스 캐필러리를 이용하여 추력 모델을 만든 후 추력을 측정하였다. 이와 더불어 extrude shape의 노즐을 갖는 마이크로 추력 장치를 PMMA(Polymethyl methacrylate)를 이용하여 공정하였으며, 매니스커스의 형상 변화를 관찰하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2631-2636
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• 2008

The most components and piping of the secondary side of domestic nuclear power plants were manufactured carbon-steel and low-alloy steel. Flow accelerated corrosion leads to wall thinning (metal loss) of carbon steel components and piping exposed to the flowing water or wet steam of high temperature, pressure, and velocity. The feedwater heaters of many nuclear power plants have recently experienced sever wall thinning damage, which increases as operating time progress. Several nuclear power plants in Korea have also experienced wall thinning damage in the shell wall around the impingement baffle. This paper describes the comparisons between the numerical analysis results using the FLUENT code and the experimental results based on down-scaled experimental facility. The experiments were performed based on several types of impingement baffle plates which are installed in low pressure feedwater heater.