• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.87-94
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• 1992

Film boiling heat transfer characteristics in liquid-liquid systems are studied experimentally. Liquid gallium as a heating liquid, n-pentane, freon-113, and ethanol are used as boiling liquids. In gallium-n-pentane and gallium-freon-113 systems the minimum film boiling point occurred at higher temperature than those observed in copper-boiling liquid systems. However MFB point occurred almost at the same temperature for the case of ethanol. This difference are due to the effects of contact angle and interfacial agitations in gallium-boiling liquid systems. Film boiling heat transfer rate, for the gallium-boiling liquid systems considered in this work, found to be approximately 10% higher than those in copper-boiling liquid systems, whose main cause is believed to be gallium-boiling liquid interfacial agitations affected by the density ratio between gallium and boiling liquid.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.4
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• pp.44-51
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• 2003

By blending of various low boiling point oxygenated agents to lower grade fuels, significant improvements were simultaneously obtained in smoke, CO, PM, SOF and BSEC. Especially, our trends were remarkably obtained by retarding injection timing, by decreasing boiling point and increasing blending contents of additives in case of oxygenated agents rather than non-oxygenated agents. Also, it was revealed that when 20vo1.% DMM added to high viscosity fuels and injection timing was retarded, NOx-smoke trade off relationship was much better than that of ordinary diesel fuel. Thus, lower grade fuels with high viscosity could be expected to be used efficiently and cleanly in diesel operation by blending low boiling point oxygenates.

• Journal of Environmental Science International
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• v.5 no.6
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• pp.749-755
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• 1996

In order to grasp a characterization of low boiling point chlorinated organic compounds, this study which were carried out at the 8 stations for precipitation samples in the Pusan area during the period from February to September 1995. As a result, low boiling chlorinated organic compounds were estimated that it was dissolved by a portion of precipitation, and it be able to shift at the surface of the each. Concentration of low boiling point chlorinated organic compounds in precipitation are increased with increase of temperature, and estimated that air pollution compounds of as a rule in atmosphere.

• Journal of Science Education
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• v.39 no.3
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• pp.446-456
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• 2015

We have analyzed affecting factors of boiling point measurement and proposed to improve these after identifying errors of boiling point experiment in 7th grade science textbooks of 2009 revised curriculum. In the result of analyzing affecting factor of boiling point measurement for nine kinds of science textbooks, we have identified six affecting factors like as types of thermometer, heating instrument, sealing or not of stopper, position of thermometer, shape of container, and volume ratio of material and container. When performing experiment of boiling point measurement, we identified the best results when heating with a hot plate, positioning thermo sensor of MBL near neck branch after filling and sopping 10% volumes of material in round bottom flask. Based on this result, we have compared nine kinds of 7th grade science textbooks and found many errors that must be corrected in most of textbooks. Therefore it should be improved the experiment of science textbooks to enhance the understanding of students and to prevent from misconceptions for boiling point measurement.

• Food Science and Preservation
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• v.4 no.3
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• pp.337-341
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• 1997

Texture is an important quality factor of processed chestnut products, which changes depending on the conditions of boiling process. The conventional boiling process consists of three stage(1st : 70 minutes at 60$^{\circ}C$; 2nd : 20minutes at 70$^{\circ}C$; 3rd : 80minutes at 98$^{\circ}C$). To improve the conventional boiling process of processed chestnut products, we investigated the changes of texture at different stages of boiling process and undertook the optimization of boiling process by response surface method on heating times of 2nd and 3rd heating, and amount of softening agent. The initial hardness and cohesiveness, the most important textural characteristics of chestnut, were 7.876kg and 0.189, respectively. In the third boiling stage, hardness decreased to 0.313kg and cohesiveness increased to 0.310. Using response surface method the minimum point of hardness and maximum point of cohesiveness was examined and model equations for predicting the changes of hardness and cohesiveness in the optional boiling condition were developed.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.454-465
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• 2015

The goal of this study is to investigate pre-service chemistry teachers’ understanding of the boiling process of a liquid mixture. We surveyed 65 students in the chemistry program of the College of Education about the boiling point of a 50%(by mole) ethanol aqueous solution and the temperature changes during heating. We then interviewed 9 of these students. According to the survey results, the percent of the pre-service teachers who thought that the boiling point of the ethanol solution would be ‘between the boiling points of ethanol and water (78-100 ℃)’ and ‘the same as that of ethanol’ were 52.3% and 35.4%, respectively. The majority of those who stated the former explained that the boiling point of the ethanol solution increased due to the effects of attraction or blocking by water molecules. Most of those who believed the latter explained that physical properties such as the boiling point would not be changed by the addition of water. With regard to the temperature change during heating, 69.2% of the teachers thought that the temperature would increase gradually while boiling, which some thought resulted from the increasing amount of water in the solution as the ethanol boiled off. Others thought that two temperature plateaus would be observed as each component of the liquid mixture underwent phase transition at its specific boiling point. When asked about the particle model of the gas phase during the boiling and evaporation process, some students drew both ethanol and water during evaporation but only ethanol when boiling. We discussed several alternative concepts of pre-service chemistry teachers about the boiling process of liquid mixtures and ways to improve their understanding.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.252-264
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• 2002

In this study, the experimental apparatus for boiling point and melting point in science textbooks of various curriculums were analyzed. Science teachers' views on the difference between the experimental value and the value written in textbooks were inquired, too. Their views on the experimental apparatus, nd results of freezing point,melting point, boiling point, fractional distillation, and thermometer calibration were also investigated. The results of this study showed that the types of experimental apparatus for boiling point and melting point were somewhat dif-ferent with science textbooks and curriculum. The teachers' views were also various according to their background. In the experiment of the fractional distillat ion, a large number of teachers recognized mismatch between the exper-imental value and the value written in textbooks as mistake of textbook contents or problem of experiment itself. The teachers of chemistry background take higher recognition of the requirement of thermometer calibration than those of non-chemistry background in middle school.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.42-51
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• 2014

An experiment was conducted to study fuel injection characteristics of high boiling point test fuels (HBPTF), which are newly developed with higher boiling points than conventional aviation fuels, for various injection pressures when the fuel was heated to the temperature higher than their boiling points. The injection characteristics with elevating fuel temperature were quantified by the flow coefficient (${\alpha}$) and the cavitation number ($K_c$), and it was found that the trends between ${\alpha}$ and $K_c$ for various fuels were very similar with each other. In addition, compared with a conventional fuel, HBPTFs not only have higher fuel temperatures at which the effect of fuel boiling on the injection initiates, but also are less affected by the fuel boiling inside the injectors at temperatures over the boiling point.

• Journal of Energy Engineering
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• v.13 no.1
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• pp.20-27
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• 2004

In the study, the effect of low boiling point oxygenates in high viscous fuels on the exhaust emissions has been investigated for a single cylinder DI diesel engine. It was tested to estimated change of engine performance and exhaust emission characteristics for the base fuels and low boiling point oxygenates blended fuel which have six kinds of fuels and various mixed rates. The results of the study may be con eluded as follows By blending of various low boiling point oxygenated agents to lower grade fuels, significant improvements were simultaneously obtained in smoke, CO, PM, SOF and BSEC. Especially, these trends were remarkably obtained by retarding injection timing, by decreasing boiling point and increasing blending contents of additives in case of oxygenated agents rather than non-oxygenated agents. Also, it was revealed that when 20 vol.％ DMM added to high viscosity fuels and injection timing was retarded, Nox-smoke trade off relationship was much better than that of ordinary diesel fuel. Thus, lower grade fuels with high viscosity could be expected to be used efficiently and cleanly in diesel operation by blending low boiling point oxygenates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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• pp.612-619
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• 2003

This work experimentally studies the fundamental mechanisms by which the ultrasonic vibration enhances convection and pool boiling heat transfer. A thin platinum wire is used as both a heat source and a temperature sensor. A high speed video imaging system is employed to observe the behavior of cavitation and thermal bubbles. It is found that when the liquid temperature is below its boiling point, cavitation takes place due to ultrasonic vibration while cavitation disappears when the liquid reaches the boiling point. Moreover, when the gas dissolved in liquid is removed by pre-degassing, the cavitation arises only locally. Depending on the liquid temperature, heat transfer rates in convection, subcooled boiling and saturated boiling regimes are examined. In convection heat transfer regime, fully agitated cavitation is the most efficient heat transfer enhancement mechanism. Subcooled boiling is most enhanced when tile local cavitation is induced after degassing. In saturated boiling regime, acoustic pressure is shown to be a dominant heat transfer enhancement mechanism.