• Carbon letters
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• 제9권4호
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• pp.289-293
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• 2008

Naphtha Cracking Bottom (NCB) oil was heat reformed at various reforming temperature and time, and the volatile extracts were characterized including yields, molecular weight distributions, and representative compounds. The yield of extract increased as the increase of reforming temperature ($360{\sim}420^{\circ}C)$ and time (1~4 hr). Molecular weight of the as-received NCB oil was under 200, and those of extracts were distributed in the range of 100-250, and far smaller than those of precursor pitches of 380-550. Naphtalene-based compounds were more than 70% in the as-received NCB oil, and most of them were isomers of compounds bonding functional groups, such as methyl ($CH_{3^-}$) and ethyl ($C_2H_{5^-}$). When the as-received NCB oil was reformed at $360^{\circ}C$ for 1 hr, the most prominent compound was 1,2-Butadien, 3-phenyl- (24.57%), while naphthalene became main component again as increasing the reforming temperature.

• Tribology and Lubricants
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• 제40권2호
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• pp.39-46
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• 2024

The Morton effect (ME) is an instability phenomenon occurring in rotating machineries supported by fluid film bearings and is induced by the thermal deformation of the overhung mass, which is a part of the rotating shaft. Herein, we describe the ME during the high-speed balancing test of a 20 MW class steam turbine. Additionally, to predict the rotating speed at which the ME occurs, we apply the sensitivity vector theory for the steam turbine. During the operation of the steam turbine, we observe a continuous increase in vibration and hysteresis near the rated speed, which is typical of the ME. Increasing the temperature of the lubricating oil supplied to the bearings from 40 to 60℃ suppresses the occurrence of the ME. The rotordynamic analysis for the steam turbine suggests the existence of a mode in which the overhung mass undergoes significant deformation near the rated speed, and we presume that such a mode will increase the occurrence of the ME. The predicted rotating speed of ME occurrence, obtained through the sensitivity vector method, correlates with the test results. Moreover, increasing the temperature of the supplied lubricating oil mitigates the occurrence of ME by reducing the sensitivity between the temperature deviation vector and unbalance mass vector.

• 접착 및 계면
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• 제3권1호
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• pp.20-23
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• 2002

The wetting properties of an uncured epoxy resin on both clean and oiled, galvanised steel have been studied. Since the polymer is very viscous at ambient temperature, and also with an aim to simulate industrial conditions, the spreading of drops of resin during a heating cycle (temperature increase at $10^{\circ}C/min$) was recorded and analysed. On clean steel, a contact angle, ${\theta}$, vs time, t, plot shows sigmoidal behaviour, whereas on the oiled substrate, spreading almost ceases in an intermediate stage. This strange behaviour is attributed to significant oil absorption by the polymer.

• 설비공학논문집
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• 제20권5호
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• pp.357-363
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• 2008

In order to investigate $CO_2$ heat transfer coefficient and pressure drop by PAG oil concentration during $CO_2$ evaporation, the experiment on evaporation heat transfer characteristics in a horizontal micro-fin tube was performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes($400{\sim}1200\;kg/m^2s$), heat fluxes($10{\sim}30\;kW/m^2$) and saturation temperatures ($-5{\sim}5^{\circ}C$), and PAG oil concentration($0{\sim}5\;wt%$). The variation of the heat transfer coefficient was different in accordance with the oil concentration. With the increase of the oil concentration, the evaporation heat transfer coefficient decreased and the delay of dryout by oil addition was found. Pressure drop increased with the increase of the oil concentration and heat flux, and the decrease of saturation temperature.

• Korean Chemical Engineering Research
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• 제47권1호
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• pp.46-53
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• 2009

본 연구에서는 비이온 계면활성제 $C_{12}E_5$ 수용액과 비극성 탄화수소 오일 시스템에 대한 상평형 및 동적 거동 실험을 수행하였다. 온도를 증가시킴에 따라 oil-in-water(O/W) microemulsion(${\mu}E$)이 excess 오일상과 평형을 이루는 2상 영역으로부터 middle-phase ${\mu}E$이 excess water, excess 오일상과 각각 평형을 이루는 3상 영역을 거쳐서 water-in-oil(W/O) ${\mu}E$이 excess 물상과 평형을 이루는 2상으로 전이되었다. 또한 탄화수소 오일의 사슬 길이가 증가할수록 상전이 온도가 증가하였다. O/W ${\mu}E$이 존재하는 낮은 온도 조건에서는 비극성 오일의 종류와 상관없이 오일이 계면활성제 마이셀에 의하여 가용화되어 시간에 따라 크기가 선형적으로 감소하였다. 한편 middle-phase ${\mu}E$을 포함한 3상이 형성되는 조건에서는 매우 낮은 계면장력으로 인하여 오일이 수용액 상에 빠른 속도로 가용화되었고 작은 drop 형태로 유화되었다. 반면에 W/O ${\mu}E$의 2상을 형성하는 온도에서는 과포화로 인하여 일어나는 자발적 유화 현상과 물과 계면활성제의 오일상으로의 확산으로 인한 오일의 크기가 증가하였다. 비극성 탄화수소 오일과 계면활성제 수용액 사이의 시간에 따른 계면장력을 $25^{\circ}C$에서 측정한 결과, 탄화수소 오일의 사슬 길이가 증가함에 따라 평형에서의 계면장력 값과 평형에 도달하는데 소요되는 시간이 모두 증가하였다.

• 한국식품과학회지
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• 제29권2호
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• pp.261-265
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• 1997

상업적인 마요네즈의 원료유로서 이중분별 팜올레인유(IV 65, 이하 팜유)의 사용 가능성을 알아보기 위하여, 마요네즈의 원료유로서 일반적으로 사용되는 식물유인 대두유와 팜유를 소정의 비율로 혼합한 식물유의 산화안정성, 저온안정성 등에 대해 비교하였다. 식물유의 산화안정성을 랜시매트법에 의한 유도기간으로 비교한 결과, 팜유는 26.9시간으로서 대두유 13.4시간 보다 두배 정도 길었고, 팜유와 대두유를 혼합하였을 때는 팜유의 비율이 높을수록 유도기간이 긴 것으로 나타났다. 저온에서의 안정성의 경우, 팜유가 대두유에 비해서 매우 불안정하였으며, 혼합유에서는 팜유의 비율이 증가함에 따라 안정성이 감소하였으나, 혼합유 중의 팜유비율이 20%보다 적을 경우에는 냉각시험을 통과하였으며, 이들 혼합유를 사용한 마요네즈의 내한성은 대두유만을 사용한 마요네즈와 유사하였다. 원료유로서 대두유에 팜유를 15% 비율로 혼합한 식용유를 사용한 마요네즈는 대두유만을 사용한 마요네즈에 비하여 고온 저장 중의 산화안정성이 증가하고, 풍미 변화가 적은 것으로 나타났다. 이러한 결과는 마요네즈의 원료유로서 팜유의 사용가능성을 제시해 주었으며, 팜유의 혼합 사용에 의해 상업적인 마요네즈의 산화안정성을 개선하고 풍미 변화를 줄일 수 있을 것으로 기대되었다.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1153-1163
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• 2002

A transient analysis on temperatures of fuel and oil in hydraulic and lubrication systems in an aircraft was studied using the finite difference method. Numerical calculation was performed by an explicit method with modified Dufort-Frankel scheme. Among various missions, air superiority mission was considered as a mission model with 20% hot day ambient condition in subsonic region. The ambience of the aircraft was assumed as turbulent flow. Convective heat transfer coefficient were used in calculating heat transfer between the aircraft surface and the ambience. For an aircraft on the ground, an empirical equation represented as a function of free-stream air velocity was used. And the heat transfer coefficient for flat plate turbulent flow suggested by Eckert was employed for in-flight phases. The governing equations used in this analysis are the mass and energy conservation equations on fuel and oils. Here, analysis of fuel and oil temperature in the engine was not carried out. As a result of this analysis, the ground operation phase has shown the highest temperature and the largest rate of temperature increase among overall mission phases. Also, it is shown that fuel flow rate through fuel/oil heat exchanger plays an important role in temperature change of fuel and oil. This analysis could be an important part of studies to ensure thermal stability of the aircraft and can be applicable to thermal design of the aircraft fuel system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.398-403
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• 2000

Experimental study on the porous ceramic burner for oil burning has been performed. Temperature profile of the combustor and CO and NOx emission have been obtained for with and without porous ceramic plate. It is found that very uniform and high temperature region with porous ceramic plate can be realized due to high radiation emission from the plate and also obtained lower CO and soot particulate emission, when compared to the conventional burner. When this burning method is applied to conventional boiler of small heating capacity, it is found that near 6 and 7 percent increase in thermal efficiency could be obtained without a proper calibration for optimization.

• 설비공학논문집
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• 제19권4호
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• pp.313-320
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• 2007

In this paper, the experimental study has been carried out to investigate the reliability lifetime of two bearing units based on the oil temperature. Measurements for the oil temperature as well as the bearing temperature during normal operation were performed to study the effects of oil viscosity and oil submergence percentages in the two bearing units. The optimal lubrication condition to increase the lifetime of the bearing unit A was found that its viscosity and submergence percentage were VG32 and 25%, respectively. For the bearing unit B, when the oil viscosity and submergence percent were VG32 and 75%, the lubrication condition was the most efficient. Finally, the adjusted rating times of both the bearing units were calculated to be over 28,000 h, which is greater than the minimum adjusted rating times of 25,000 h. Therefore, they satisfied the regulated lifetime of API 610.

• 에너지공학
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• 제12권3호
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• pp.216-222
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• 2003

실험실 규모의 진공 증발 수분 제거 시스템을 이용하여, 압력, 윤활유의 온도, 초기 수분농도 및 윤활유 분사 노즐의 형태 등 폐윤활유 속에 포함된 수분 제거 성능에 영향을 미치는 각각의 운전 변수들에 대한 실험적인 연구를 수행하였다. 연구의 결과 압력 및 폐윤활유 온도의 증가는 수분 제거 성능에 매우 중요한 변수임을 확인하였으며, 또한 진공 증발실로 폐윤활유를 분사하기 위한 노즐의 형태는 다공성 매질의 노즐 형상인 경우가 가장 우수한 수분 증발 성능을 나타내었다.