• 설비공학논문집
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• 제3권1호
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• pp.51-60
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• 1991

The aim of this study is to investigate the heat transfer characteristics in the transient cooling process of a high temperature wall. The slow transient cooling experiment was carried out with a copper block of high thermal capacity. The results of these experiments are as follows. 1. Temperature histories measured by the thermocouple, which is 0.99, 2.00, 2.99mm from the heat transfer surface showed monotonous during the cooling process. These variation are the curves of typical temperature histories in film-boiling, transition-boiling, and nucleate-boiling regions. 2. The temperature histories were measured by thermocouple installed in the copper block. The variations of the surface heat fluxes and surface temperature were computed from the numerical solution method TDMA from the measured temperature histories for radial position one dimensional heat transfer inverse problem. The boiling curves were found by the computed temperature histories. 3. The rewetting point which starts to change from film boiling to nucleate boiling is not connected with the mass velocity and it were found that the temperature of rewetting point indicated about $100^{\circ}C$. 4. The heat flux of rewetting point was about $10^5Kcal/m^2h$, at that time, the heat transfer coeficient indicated about $1000Kcal/m^2h^{\circ}C$ irrelevent to mass velocity. 5. The wall superheat decreases as the pressure increases. But I found that rewetting point appeared under higher condition in the wall temperature.

• 한국안전학회지
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• 제35권5호
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• pp.128-136
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• 2020

In the present experimental study, the effect of water-based iron(III) oxide nanofluid on the MFB(Minimum Film Boiling) point during quenching was investigated. As the highly heated test specimen, the cylindrical stainless steel rod was used, and as the test fluids, the water-based iron(III) oxide nanofluids of 0.001 and 0.01 vol% concentrations were prepared with the pure water. To examine the effect of location in the test specimen, the thermocouples were installed at the bottom and middle of wall, and center in the test specimen. Through a series of experiments, the experimental data about the influences of nanofluid concentrations, the number of repeated experiments, and locations in the test specimen on the reaching time to MFB point, MFBT(Minimum Film Boiling Temperature), and MHF(Minimum Heat Flux) were obtained. As a result, with increasing the concentration of nanofluid and the number of repeated experiments, the reaching time to MFB point was reduced, but the MFBT and MHF were increased. In addition, it was found that the effect of water-based iron(III) oxide nanofluid on the MFB point at the bottom of wall in the test specimen was observed to be greater than that at the middle of wall and center. In the present experimental ranges, as compared with the pure water, the water-based iron(III) oxide nanofluid showed that the maximum reduction of reaching time to MFB point was about 53.6%, and the maximum enhancements of MFBT and MHF were about 31.1% and 73.4%, respectively.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.67-76
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• 2009

The development of a variety of methods like AM1, PM3, PM5 and DFT now allows the calculation of atomic and molecular properties with high precision as well as the treatment of large molecules with predictive power. In this paper, these methods have been used to calculate a number of quantum chemical descriptors (like Klopman atomic softness in terms of $E_n^{\ddag}\;and\;E_m^{\ddag}$, chemical hardness, global softness, electronegativity, chemical potential, electrophilicity index, heat of formation, total energy etc.) for 75 alkanes to predict their boiling point values. The 3D modeling, geometry optimization and semiempirical & DFT calculations of all the alkanes have been made with the help of CAChe software. The calculated quantum chemical descriptors have been correlated with observed boiling point by using multiple linear regression (MLR) analysis. The predicted values of boiling point are very close to the observed values. The values of correlation coefficient ($r^2$) and cross validation coefficient ($r_{cv}^2$) also indicates the generated QSPR models are valuable and the comparison of all the methods indicate that the DFT method is most reliable while the addition of Klopman atomic softness $E_n^{\ddag}$ in DFT method improves the result and provides best correlation.

• 한국식품과학회지
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• 제22권4호
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• pp.486-491
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• 1990

마늘을 장기 저장하고 또 새로운 향신료로서 개발하기 위한 연구의 일환으로 박피한 마늘을 전기 착즙기로 착즙한 다음 정제하여 마늘 착즙을 제조한 후 증발시켜 농축 마늘즙을 제조하였으며 그 일환으로 마늘 착즙의 성분 조성 및 비점 상승 추정에 대한 연구가 행해졌다. 마늘 착즙의 주성분은 수분 68.01%, 조단백질 6.50%, 탄수화물 25.39%였고, 착즙 수율은 박피한 통마늘 기준으로 49.50%(w/w)였으며 마늘 착즙의 밀도는 고형물 농도 $32{\sim}65^{\circ}Brix$에서 $1,107{\sim}1,243kg/m^3$였다. 마늘 착즙의 비점 상승은 농도의 증가에 따라 지수함수적으로 상승하였으며 고형물 농도 $32{\sim}65^{\circ}Brix$ 범위에서 $1.43{\sim}6.70^{\circ}C$ 정도 상승하였다. 고형물 농도와 증발기의 압력을 변수로 하는 비점 상승 추정식은 다음과 같았으며 측정치를 기준으로 한 오차는 7% 이내였다. $BPR=1.4105.\;P^{0.1338}.\;exp(0.0357.\;X_5-1.3925)$

• 펄프종이기술
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• 제48권1호
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• pp.119-126
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• 2016

In this study, we separated the lignin from the wood by using the high boiling point solvent for developing more environmental friendly pulping method. High boiling point solvents as Ethers, glycols and ketones were used to remove the lignin in the pine wood meals. The Yield and lignin content of residual wood meals was reduced according to the input of the catalyst. Me-C, E-Ca, TEG and MIBK had the best delignification rate of 9 kinds of high-boiling point solvents. At the hydrolysis ratio of the selected solvents, The TEG was highest remain ratio of carbohydrates and the E-Ca was lowest remain ratio of lignin. And the Me-C was most excellent lignin hydrolysis ratio at the low catalyst. The selectivity of delignification of Me-C, E-Ca, TEG and MIBK solvents were 49.6, 49.9, 53.8 and 53.1%, respectively, and its values were similar to those of the commercial Kraft Pulp.

• 태양에너지
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• 제19권2호
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• pp.45-56
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• 1999

The performance of vertical and horizontal tubes with extended surface of rectangular and triangular cross section was investigated theoretically for boiling heat transfer. A simple method for numerical program assuming one-dimensional heat flow was used to predict the performance of these extended surface tubes. The object of this study was to predict the effects of the height, thickness, numbers and, clearance of the extended surface on boiling heat transfer. The results showed that extended surfaces are quite effective as compared to plane surfaces especially near the bum-out point and to promote heat flux in boiling heat transfer.

• 한국과학교육학회지
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• 제33권7호
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• pp.1385-1402
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• 2013

이 연구는 끓는점 오름에 대한 내용표상화 활동과 모의수업 실행을 통해서 예비교사의 PCK를 분석하였다. 예비교사의 지식을 PCK 요소에 따라 분석한 결과, 대부분의 예비교사는 끓는점 오름에 대한 개념적인 이해를 중시하였는데, 일부는 끓는점 오름 현상을 과학적인 시각으로 이해하고, 수식을 도구로 사용하며, 실생활에 적용되는 경험을 통해 학습 동기를 얻게하는 과학 교수 지향도 보였다. 예비교사는 끓는점 오름에 관하여 가르쳐야 할 중요한 내용의 대부분을 개념 이해를 위해 습득해야 할 지식으로 제시했으며, 과학적 사고나 탐구능력 신장을 위한 내용은 나타나지 않았다. 또한 교과서 내용의 수준과 전개 순서에 의존하는 경향을 보였으며 일부는 교과서 편집상 강조되어있는 용어나 자료를 학습할 내용으로 여기거나, 예제 문제의 풀이를 학습 목표로 보는 경우도 있었다. 학생 이해에 대한 지식은 부족한 것으로 나타났는데, 실제 교수 경험이 없는 예비교사들은 자신의 학습 경험을 바탕으로 학생 수준을 간접적으로 이해하려고 시도하므로, 예비교사교육과정에서 오개념 자료 등을 적극적으로 활용할 필요가 있다. 교수 전략과 평가에 대한 지식은 다른 요소에 비해 피상적으로 표현되었는데, 목표와 연계된 방법을 고민하기 보다는 순환학습과 발견학습 같은 모형의 적용만을 언급하거나 일반적인 평가 방법을 나열하는데 그쳤다.

• 한국해양공학회지
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• 제6권2호
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• pp.35-40
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• 1992

A recently developed new technique for measuring the fraction of wetted area has applied to pool boiling of water. The basis of the new applied technique of ultrasonic makes use of the reflection of ultrasonic from the vapour surface to measure the fraction of wetted area values. The results are the measured fraction of wetted area values in nucleate and transition boiling and the pool boiling curve for water under steady state conditions. The measurement of this paper shows a fraction of wetted areaf around 0.98 at the critical heat flux for water.

• 대한기계학회논문집B
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• 제24권4호
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• pp.485-494
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• 2000

The purpose of this paper is to investigate a critical heat flux(CHF) during forced convective subcooled and saturated boiling in free water jet system impinged on a rectangular heated surface. The surface is supplied with subcooled or saturated water through a rectangular jet. Experimental parameters studied are a width of heated surface, a height of supplementary water and a degree of subcooling. Incipient boiling point is observed in the temperature of 6${\~}8^{\circ}C$ of superheat of test specimen. CHF depends on jet velocity for various boiling-involved coolant system. CHF also is proportional to the nozzle exit velocity to the power of n, where n is 0.55 and 0.8 for subcooled and saturated boiling, respectively. CHF is enhanced with a higher jet velocity, higher degree of subcooling and smaller width of a heated surface.

• 한국시뮬레이션학회논문지
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• 제4권1호
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• pp.121-130
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• 1995

This paper deals with modeling and simulation of an industrial benzene-toluene-xylene plant. Because the fractionation unit of benzene-toluene-xylene plant has a narrow range of boiling point and doesn't have any sidecut and side reboiler, we employed boiling point estimation method in the modeling and simulation of the plant. Soave-Redlich-Kwong equation was used in the computation of thermodynamical properties. We solved resulting nonlinear equations by using Newton-Raphson method which is known to show fast convergence. Results of simulation showed good agreement with actual plant operation data.