• 동아시아식생활학회지
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• 제24권1호
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• pp.62-69
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• 2014

Jungkwa is a traditional Korean dessert preserved in honey or sucrose. This study was carried out to investigate the antioxidant activities and quality characteristics of Rehmannia glutinosa Jungkwa (RJ). RJ was prepared after six repeated cycles of boiling-cooling. After blanching fresh Rehmannia glutinosa (600 g) for 5 min at $100^{\circ}C$, Rehmannia glutinosa was boiled in sucrose syrup (sucrose 720 g in water 600 g) for 60 min and then cooled for 24 hr. Moisture, pH and color values of lightness, redness and yellowness in the Hunter color system of Jungkwa decreased as the number of boiling-cooling cycles increased, whereas acidity, $^{\circ}Brix$ and reducing sugar contents of syrup increased. Total phenol content increased in by the 6th boiling-cooling cycle. Antioxidant activities, including DPPH and hydroxyl radical scavenging activities, increased in RJ by the 6th boiling-cooling cycle. Based on these results, the antioxidant activities of Rehmannia radix Jungkwa was improved according to an increasing number of boiling-cooling cycles due to increased total phenol contents.

• 설비공학논문집
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• 제14권6호
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• pp.441-449
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• 2002

Single-phase convection and partial nucleate boiling in free-surface and submerged jet impingements of subcooled water ejected through a 2-mm-diameter circular pipe nozzle were investigated by local measurements. Effects of jet velocity and nozzle-to-imping-ing surface distance as well as heat flux on distributions of wall temperature and heat transfer coefficients were considered. Incipience of boiling began from far downstream in contrast with the cases of the planar water jets of high Reynolds numbers. Heat flux increase and velocity decrease reduced the temperature difference between stagnation and far downstream regions with the increasing influence of boiling in partial boiling regime. The chance in nozzle-to-impinging surface distance from H/d=1 to 12 had a significant effect on heat transfer around the stagnation point of the submerged jet, but not for the free-surface jet. The submerged jet provided the lower cooling performance than the free-surface jet due to the entrainment of the pool fluid of which temperature increased.

• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1662-1669
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• 2005

Boiling heat transfer characteristics of a two-phase closed thermosyphons with various helical grooves are studied experimentally and a mathematical correlation is developed to predict the performance of such thermosyphons. The study focuses on the boiling heat transfer characteristics of two-phase closed thermosyphons with copper tubes having 50, 60, 70, 80, 90 internal helical grooves. A two-phase closed thermosyphon with plain copper tube having the same inner and outer diameter as those of grooved tubes is also tested for comparison. Water, methanol and ethanol are used as working fluid. The effects of the number of grooves, various working fluids, operating temperature and heat flux are investigated experimentally. From these experimental results, a mathematical model is developed. In the present model, boiling of liquid pool in the evaporator is considered for the heat transfer mechanism of the thermosyphons. And also the effects of the number of grooves, the various working fluids, the operating temperature and the heat flux are brought into consideration. A good agreement between the boiling heat transfer coefficient of the thermosyphon estimated from experimental results and the predictions from the present mathematical correlation is obtained. The experimental results show that the number of grooves, the amount of the working fluid and the various working fluids are very important factors for the operation of thermosyphons. Also, the thermosyphons with internal helical grooves can be used to achieve some inexpensive and compact heat exchangers in low temperature.

• 설비공학논문집
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• 제17권8호
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• pp.714-721
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• 2005

The water jet impingement cooling with boiling is one of the techniques to remove heat from high heat flux equipments. The configuration of surface roughness is one obvious condition of affecting the performance on heat transfer in nucleate boiling, The present study investigates the water jet impinging single-phase convection and nucleate boiling heat transfer for the effect of surface roughness to enhance the heat transfer in free surface and submerged jet. The distributions of the averaged wall temperature as well as the boiling curves are discussed. Jet velocities are varied from 0.65 to 1.7 m/s. Surface roughness by sand blast and sand paper varies from 0.3 to 2.51 ${\mu}m$ and cavity shapes on surface are semi-circle and v-shape, respectively The results showed that higher velocity of the jet caused the boiling incipience to be delayed more. The incipient boiling and heat transfer increase with increasing surface roughness due to a large number of cavities of uniform size.

• 설비공학논문집
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• 제23권7호
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• pp.498-504
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• 2011

As the electronic industry rapidly develops, the heat flux from state-of-the-art electronics increases up to $10^6\;W/m^2$. For this reason, the development of a new cooling technology for high heat flux applications is strongly required. Recently, some cooling technologies using boiling and condensation of working fluid are being adopted to overcome such a technical barrier. In the present study, a smooth boiling surface ($14{\times}14\;mm^2$) was immersed in FC-72 and its vapor was condensed by four different types of condensation surfaces ($30{\times}30\;mm^2$ base). The condensing surfaces were composed of a smooth surface and $1{\times}1\;mm^2$ pin-finned surfaces of 2 mm height with 0.3, 0.5 and 1 mm array spacing. Boiling and condensing characteristics were investigated in detail on their combinations of boiling and condensing surfaces. For a smooth boiling surface the results obtained showed that the pin-finned condensing surface with 1 mm array spacing yielded the best performance and the smooth condensation surface did the worst. Furthermore hysteresis phenomena could be reduced by using enhanced condensing surfaces.

• 설비공학논문집
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• 제16권10호
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• pp.977-983
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• 2004

An experimental study on saturated flow boiling heat transfer of R113 was peformed in a vertical narrow rectangular channel with offset strip fins. Two-phase pressure gradients and boiling heat transfer coefficients in an electrically heated test section were measured in the range of quality $0{\sim}0.6$, mass flux $17{\sim}43kg/m^{2}s$, and heat flux of $500{\sim}3,000W/m^2$ Two-phase friction multipliers were determined as a function of Lockhart-Martinelli parameter. Local boiling heat transfer coefficients were analysed in terms of mass flux, heat flux and local vapor quality. Correlation for boiling heat transfer coefficients was proposed, which was in good agreement with experimental data.

• 과학교육연구지
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• 제39권3호
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• pp.446-456
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• 2015

2009 개정 7학년 과학 1 교과서에 제시된 끓는점 실험을 할 때 측정에 영향을 미치는 요인을 분석하였으며, 실험을 통해 교과서에 제시된 실험 방법의 오류를 확인한 후 이를 개선하기 위한 방안을 제안하였다. 2009 개정 7학년 과학 1 교과서 9종에 제시된 끓는점 측정 실험을 분석하여 끓는점에 영향을 미치는 요인을 찾아보았더니 온도계의 종류, 가열 도구, 마개 밀폐 여부, 온도계의 위치, 가열 용기의 모양, 물질과 가열용기의 부피비와 같은 6종류의 요인을 확인하였다. 물질의 끓는점을 측정하는 실험을 수행할 때, 둥근바닥 플라스크의 10%만 물질로 채운 후 MBL 온도 센서를 가지 부근에 위치하게 하고, 마개를 막아 핫플레이트로 가열하는 것이 가장 효과적인 결과를 나타내는 것을 확인하였다. 이를 토대로 2009 개정 7학년 과학 1 교과서 9종과 비교하였더니 대부분의 교과서에서 수정되어야 할 점이 많은 오류가 있음을 발견하였다. 따라서 끓는점 측정에 대한 학생들의 학습 이해도를 높이고 오개념을 방지하기 위해 과학 1 교과서에 제시되어 있는 실험들이 보다 정확하게 개선되어야 할 것이다.

• 대한한의학방제학회지
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• 제8권1호
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• pp.11-37
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• 2000

This is a study on the methods of decocting prescriptions in SANGHANRON (傷寒論), and after this, numbers of results have been obtained. SANGHANRON was written by Chang-Ki (張機) in the 2nd century, so it reflexes the usage of prescriptions of previous age indirectly. And gave affects on the methods of decocting prescriptions to the oriental medicine doctors of next generation.Berore Han-DYnasty(漢代), there were not so many publications connected with Oriental Medicine. Besides, some books couldn't hand down to next generation due to the gap of time and space. As time goes by, letters in medical books changed little by little, so contents connected with decocting methods changed too. The effects of decoction and herb tea can be changed by the flexibility of methods of decocting medicines, so we have to decide what kinds of decocting methods should be taken and adapted to patients by the most effective way.In SANGHANRON, there are many kiny kinds of boiling methods, so DHAMG-Ki selected the most appropriate method considering deree and position of disease and condition of patient. But nowadays, due to inconvenient procedure of boiling and taking medicines, some methos are not in common in clinical medicin. So this study was started to look back upon the changes of decocting prescriptions and gave deffort to find out the propriety of variation of boiling prescriptions.The common method of decocting prescriptions in SANGHANRON is boiling down all the herbs at the same time. Except the commom method, there are some kinds of other methods - boiling down twice the prescription, boiling down some special herbs earlier of later than other herbs, complicated or special boiling methods of extract, etc. These kinds of decoting methods simplified as time pass by, but this expected therapeutic value. So we have to distinguish the methods -though complicated and troublesome- in clinical medicine to make perfection more perfect in treating patients, and further studies have to be followed to prove the propriety of these complicated methods.

• 한국조리학회지
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• 제15권3호
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• pp.236-247
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• 2009

소스가 창업의 성패를 좌우한다는 말이 나올 정도이며 차별화된 소스는 음식 매출을 좌우하는 것은 물론이고, 직접 판매도 가능해 앞으로 음식점 경쟁력 강화의 필수 요소라고 한다. 농후제를 사용하지 않고 설탕을 첨가한 조미액을 농축하여 사용하는 데리야끼 소스는 가열하는 시간에 따라서 소스의 색, 맛, 점도 등 주요 특성에 큰 영향을 받는다. 본 연구에서는 닭 뼈를 이용하여 데리야끼 소스를 제조할 때, 가열시간을 달리하여 제조한 데리야끼 소스의 관능평가를 통해 데리야끼 소스 제조시 기호도가 가장 좋은 가열시간을 찾아내서 산업화 하는데 기여하고자 수행하였다. 그 결과 가열시간이 증가할수록 수분 함량과 pH는 낮아지는 경향을 나타낸 반면, 당도와 점도는 증가하였다. 한편, 색도는 명도와 적색도는 8시간에서 최대치가 되었다가 이후로 낮아졌고, 황색도의 경우 가열시간에 따라 점차 낮아지는 경향을 보였다. 정량적 묘사분석의 경우 소스만 평가하였을 때는 잡냄새의 유의적인 차이가 있었으나, 동반식품을 곁들였을 때는 유의적인 차이를 보이지 않았다. 기호도 검사에서 소스만 평가하였을 때와 닭고기를 곁들였을 때는 8시간 가열한 소스가 가장 좋은 평가를 받았고, 장어를 동반식품으로 곁들인 경우에는 10시간 가열한 소스가 가장 좋은 평가를 받았다. 따라서 닭 뼈를 이용한 데리야끼 소스의 가열시간은 8~10시간(본 실험에서 설정한 제한적인 조건하에서)이 적절한 것으로 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제40권4호
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• pp.275-281
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• 2016

본 연구에서는 전산유체역학(CFD)을 이용하여 저압에서의 과냉각 비등 현상에 대한 수치해석적 연구를 수행하였다. 과냉각 비등 현상을 시뮬레이션하기 위해서 벽비등 모델을 사용하였으며, 벽비등 모델은 기포 이탈 직경, 핵 사이트 밀도 그리고 기포 이탈 빈도로 구성된 하위모델을 필요로 한다. 전산유체역학 코드 CFX는 실험 자료에 근거한 기본 모델을 제공한다. 하지만 이러한 모델은 대부분 고압조건에서 개발되었기 때문에 저압조건에서는 잘 맞지 않는 것으로 보인다. 따라서 본 연구에서는 저압조건에서 과냉각 비등 현상에 대해서 CFD의 유효성을 검토하였다. 수치해석적 결과는 기존의 실험 결과와 비교하였다. 수치해석은 질량유속 $250{\sim}750kg/m^2s$, 열유속 $0.37{\sim}0.77MW/m^2$ 그리고 출구압력 0.11 MPa범위에서 수행되었다. 저압조건에서 개발된 상관식을 적용함으로써 수치해석의 정확성을 높일 수 있었다.