• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.5
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• pp.627-633
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• 2001

Characteristics of a diesel spray impingement with the variation of ambient temperature, wall temperature and ambient pressure were investigated through shadowgraphy method by using high speed camera. The radial penetration of spray was increased with ambient temperature and wall temperature. It is resulted from the decrease of ambient gas density caused by the increase of temperature. The height of spray was also increased with ambient temperature and wall temperature, because the height of stagnate region is noticeably increased, although height of wall jet vortex is decreased. At the same ambient pressure, the area ratio of impinging spray of room temperature environment to high temperature environment was increased, as the temperature difference between room temperature and high temperature increases. And the increment of area ratio was higher at low ambient pressure than high ambient pressure.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.524-524
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• 2012

Thermal Barrier Coating (TBC)은 미사일, 로켓발사체와 같이 고온에 노출되는 장비를 열로부터 보호하기 위한 코팅이다. 일반적인 Thermal Barrier Coating (TBC)은 모재와 코팅층간의 낮은 접합력과 높은 열충격으로 인한 박리가 많이 나타난다. 그래서 접합력을 높이고, 열충격을 줄이기 위해 모재와 코팅층 사이에 본드코팅층을 만든 Duplex - Thermal Barrier Coating (Duplex-TBC)이 개발되었다. 그러나 Duplex - Thermal Barrier Coating (Duplex-TBC)은 금속재료인 본드코팅층과 세라믹재료인 탑코팅층 사이에서 박리가 많이 발생한다. 이러한 문제점을 해결하기 위해 두 가지 분말을 동시에 코팅하여 본드코팅과 탑코팅의 경계가 없는 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)의 연구가 필요하다. 본 연구에서는 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)의 열충격 특성에 미치는 진공 플라즈마 용사 조건의 영향을 조사하였다. Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)는 진공 플라즈마 용사장치를 사용하여 Cu-Cr 합금위에 코팅하였다. 거리, Carrier gas flow, 그리고 챔버 내부의 압력을 달리하여 제조하였다. 사용한 분말은 본드코팅용으로 Amdry 962와 내열 세라믹코팅을 위해 204NS를 사용하였고, 각각 분말 공급조건을 조절하여 두 분말의 비율을 달리하였다. 제조한 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC) 코팅은 전기로에서 50분간 가열한 후, 수조에서 10분간 냉각하는 열충격 실험을 통해 열차폐 성능을 평가 하였다. 이러한 과정에서 진공 플라즈마 용사 조건 및 FGM 조성과 비율이 내열충격 특성에 미치는 영향을 미세조직학적 관점에서 고찰하였다.

• Korean Journal of Food Science and Technology
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• v.39 no.6
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• pp.637-643
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• 2007

In this report, we discussed the physiochemical characteristics of corn starch during the alkali gelatinization process. Here, solubility and the amounts of eluted polysaccharides and amyloses increased in proportion to the amount of alkali added. The X-ray diffraction patterns and DSC thermogram showed that in the early stage of alkali gelatinization, crystallinity of the starch granules was disrupted as compared with heat gelatinization. This resulted in the eluted amylose content, while granule sizes were hardly changed in the alkali treated corn starch. The endotherm peak in the DSC thermogram shifted toward a higher temperature region as the degree of gelatinization increased, suggesting that the retained starch granules were more compactly crystallized during alkali gelatinization than during the heat process. Thus, we concluded that during the alkali gelatinization of corn starch, the disruption of weak particles would occur first, before swelling of the granules.

• Fire Science and Engineering
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• v.14 no.3
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• pp.13-18
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• 2000

The objective of the present work is to examine the cooling characteristics of water droplet on the unburned surface. The hot solid surface material used brass, carbon steel and copper at temperature ranging from 70 to $116^{\circ}$. the droplet size is from 2.4 mm to 3.0 mm. The CCD camera was used to record the evaporation histories of the droplets. and the evaporation time of the droplet on the hot solid surface could be determined by using frame-by-frame analysis of the video records. It is found that during the droplet evaporation process for copper the temperature remains nearly constant, whereas for carbon steel the temperature continuously decreases about $1^{\circ}$. During the droplet evaporation process on the hot solid surface, regardless of solid materials, nondimensional droplet volume decreases nondimensional evaporation time increases.

• Korean journal of food and cookery science
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• v.32 no.4
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• pp.383-389
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• 2016

Purpose: This study was conducted to evaluate the effect of rehydration and subsequent heating at high temperature on the pigments and antioxidants of dried samnamul (Aruncus dioicus) and daraesoon (Actinidia arguta). Methods: Rehydration included 16 h-soaking in cold water, and 30 min-boiling and 1 h-infusion in water. Rehydrated samnamul and daraesoon were heated at $180^{\circ}C$ for 10 or 20 min with or without perilla oil addition (10%) for cooking. Pigments and antioxidants were determined by HPLC and spectrophotometry. Results: Rehydration caused decreases in pigment and polyphenol contents, but increase in tocopherol content. Cooking by heating without addition of perilla oil resulted in increases in chlorophyll and carotenoid contents, but decreases in polyphenol and tocopherol contents. Decrease in tocopherol content by heating at $180^{\circ}C$ was reversed by the addition of perilla oil. Conclusion: This study strongly suggested that cooking of samnamul and daraesoon at $180^{\circ}C$ with perilla oil could improve color, texture, and potential health functionality by recovering the loss of antioxidants and pigments with antioxidant activity.

• Fire Science and Engineering
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• v.23 no.5
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• pp.50-56
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• 2009

Explosion limit and autoignition temperature are the major properties used to determine the fire and explosion hazards of the flammable substances. Explosion limit and autoignition temperature for safe handling of ethylene were investigated. By using the literatures data, the lower and upper explosion limits of ethylene recommended 2.6vol% and 36vol%, respectively. Also autoignition temperatures of ethylene with ignition sources recommended $420^{\circ}C$ at the electrically heated crucible furnace (the whole surface heating) and recommended about $800^{\circ}C$ in the local hot surface. The new equations for predicting the temperature dependence and the pressure dependence of the lower explosion limits for ethylene are proposed. The values calculated by the proposed equations were a good agreement with the literature data.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.6
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• pp.591-595
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• 1990

A promoting effect of ginseng saponin on the growth recovery rate of Saccharomyces rouxii which was treated by heat was confirmed in previous report(22). In order to deduce the promoting effect on the growth recovery of the heat stressed yeast, the effect of ginseng saponin on the activity and the heat stability of the amylase produced by Sacchirromyces rouxii were observed. The amylase showed the highst activity at 0.01％ of saponin. At this concentration, the activity increased about 23％ compared to the control. Furthermore, the ginseng saponin showed a protective effect against thermal inactivation of the amylase produced by Saccharomyces rouxii.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.349-354
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• 2002

쌀 소비량은 생활 수준 향상과 외식 및 식품 산업의 발달로 감소하고, 고품질 쌀을 요구하는 성향이 높아지고 있다. 현재, 고품질 쌀을 생산할 수 있는 기술과 제반 요건은 구비되어 있으나, 수확 후 건조·저장 중에 쌀의 품질이 저하된다. 특히 건조 중 품질 저하는 고온건조에 의한 동할 발생 및 과건조가 주요 원인이다. 이를 해결하기 위해 원적외선 건조 시스템에 관한 연구가 진행 중이다. 본 연구에서는 방사율이 높고, 접착성 및 내열성 등이 강한 곡물 건조기용 방사체 코팅원료를 개발하고, 이 원료를 원적외선 방사체에 코팅한 후 방사체의 형태와 크기에 따라 표면 온도 분포 및 연료 소비량 등을 측정 분석하여 방사체의 특성과 적정 조건을 규명하고자 하였다. 연구 결과를 요약하면 다음과 같다. (1) 세라믹 코팅 원료의 배합비는 세라믹분말 40%와 결합재 60%가 접착력과 가열경화 후 표면이 양호한 것으로 나타났다. (2) 노즐의 유량 및 분무각에 따른 버너의 화염길이 및 폭은 노즐유량이 증가함에 따라 증가하는 경향을 나타내었다. (3) 방사체 위치별 표면온도편차는 방사체 길이가 1350mm인 것이 작은 것으로 나타났고, 열풍유동관 직경이 Rounding type의 경우 76.3mm, Right angle type의 경우 89.1mm일 때 표면 온도편차가 적었다. (4) 연료소비량은 열 풍유동관 직경이 클수록, 방사체 길이가 길수록 증가하는 경향을 나타내었고, Right angle type이 Rounding type에 비하여 연료소비량이 약간 높은 것으로 나타났다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.6
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• pp.884-895
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• 1997

The finite element analysis for the tubular alumina liner which was shrink-fitted into a heat treated high speed steel (HSS) sleeve and subjected to high inner pressure and high temperature was performed. The parameters for the analysis were the interference between the alumina and the HSS, the temperature, the inner pressure, the coefficient of friction between the alumina and the HSS, and the taper at the sleeve ends. From the analysis, it was found that the tensile hoop stresses were decreased when the end parts of the HSS sleeve were tapered and the tensile stresses were decreased as the coefficient of friction between the alumina and the HSS was decreased. Also it was found that the alumina might be used as the structural liner for high pressure and high temperature when it was shrink-fitted into a heat treated HSS sleeve.

• Fire Science and Engineering
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• v.19 no.4 s.60
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• pp.18-25
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• 2005

In this study, numerical analysis of two-dimensional unsteady natural convection of air in a square enclosure heated from below, was performed as a basic research of fire science. SIMPLE algorithm was used to the pressure term of momentum equations in the numerical analysis. The numerical analysis were studied for the two model cases and two heat conditions, respectively, which are different with insulation of enclosures and position of heat applied. Also, the ceiling temperatures of enclosure were measured to compare the accuracy of numerical analysis, and it is found that the temperature predicted by numerical analysis were agreed well with the measurements. Streamline and isotherm of the each model case were acquired for each time step.