• 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 Power System Engineering
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• v.17 no.2
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• pp.21-28
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• 2013

Phenomenon of droplet impingement with high temperature wall needs to be investigated because atomization process of droplet and cooling process of the wall by the impingement are very important in industry, thus studies concerned with temperature of piston wall have been conducted in spray characteristics analysis of diesel engine. Hence, in this study, we defined $DT_{sat}(=T_w-T_{sat})$ superheat degree of the wall by difference between $T_w$ considering surface temperature of piston in the actual engine and $T_{sat}$ saturation temperature of the fuel and then investigated spray behavior of wall impinging with variance of the boiling process. In this study, in order to analyze wall impingement of droplet in accordance with difference of boiling condition, calculational conditions were set as $DT_{sat}=40K$(nucleate boiling), $DT_{sat}=140K$(transition boiling), and $DT_{sat}=240K$(film boiling). As a result, it can be found that fuel vapor increases and droplet mass decreases in the order of the nucleate boiling, transition boiling, and film boiling.

• Textile Coloration and Finishing
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• v.18 no.6 s.91
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• pp.69-79
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• 2006

The washing characteristics of steam jet heating process have been compared with other washing processes, such as low temperature process(standard process, below $40^{\circ}C$) and high temperature process(boiling process, up to $95^{\circ}C$) with the standard soil fabric, EPMA 105. Steam jet heating process showed almost the same washing efficiency as high maximum temperature process for pig's blood and wine. This result can be explained with the higher surface temperature of washing materials in steam jet process compared with direct boiling process. In terms of the energy and water consumption, the steam jet washing process showed significant savings compared with direct boiling type washing process.

• 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 Ocean Engineering and Technology
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• v.35 no.1
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• pp.50-58
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• 2021

The demand for eco-friendly energy is expected to increase due to the recently strengthened environmental regulations. In particular, the flow inside the pipe used in a cargo handling system (CHS) or fuel gas supply system (FGSS) of hydrogen transport ships and hydrogen-powered ships exhibits a very complex pattern of multiphase-thermal flow, including the boiling phenomenon and high accuracy analysis is required concerning safety. In this study, a feasibility study applying the boiling model was conducted to analyze the multiphase-thermal flow in the pipe considering the phase change. Two types of boiling models were employed and compared to implement the subcooled boiling phenomenon in nucleate boiling numerically. One was the "Rohsenow boiling model", which is the most commonly used one among the VOF (Volume-of-Fluid) boiling models under the Eulerian-Eulerian framework. The other was the "wall boiling model", which is suitable for nucleate boiling among the Eulerian multiphase models. Moreover, a comparative study was conducted by combining the nucleate site density and bubble departure diameter model that could influence the accuracy of the wall boiling model. A comparison of the Rohsenow boiling and the wall boiling models showed that the wall boiling model relatively well represented the process of bubble formation and development, even though more computation time was consumed. Among the combination of models used in the wall boiling model, the simulation results were affected significantly by the bubble departure diameter model, which had a very close relationship with the grid size. The present results are expected to provide useful information for identifying the characteristics of various parameters of the boiling model used in CFD simulations of multiphase-thermalflow, including phase change and selecting the appropriate parameters.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.403-406
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• 2002

A number of the experiments on the phenomenon in which the thermal energy was transferred from a hot sphere to the surrounding water through the film boiling process had been conducted. As the sphere only carried the thermal energy associated with its initially high temperature but did not contain any other thermal source, the film boiling was only driven by the decreasing temperature of the sphere and, thus, was time dependent. The results from the experiments showed that the temperature of the sphere was slowly decreased in the beginning. This corresponded to the period in which the sphere was penetrating the water surface. Later, when the sphere was fully submerged and the transition film boiling was observed over the whole surface, the temperature of the sphere was decreased relatively much faster. In the last stage, the temperature of the sphere was again slowly decreased. This was considered caused by the relatively low temperature of the sphere, which reduced and later ceased the film boiling process. In addition, the estimation of the departure rate of the steam bubbles from the film layer was also correlated for the experiments.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.2
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• pp.156-164
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• 1986

In the case of boiling on high temperature wall, vapor film covers fully or parcially the surface. This phenomenon, film boiling or transition boiling, is very important in the surface heat treatment of metal, design of cryogenic heat exchanger and emergency cooling of nuclear reactor. Mainly supposed hydraulic-thermal accidents in nuclear reactor are LCCA (Loss of Coolant Accident) and PCM (Power-Cooling Mismatch). Recently, world-wide studies on reflooding of high temperature rod bundles after the occurrence of the above accidents focus attention on wall temperature history and required time in transient cooling process, wall superheat at rewet point, heat flux-wall superheat relationship beyond the transition boiling region, and two-phase flow state near the surface. It is considered that the further systematical study in this field will be in need in spite of the previous results in ref. (2), (3), (4). The paper is the study about the fast transient cooling process following the wall temperature excursion under the CHF (Critical Heat Flux) condition in a forced convective subcooled boiling system. The test section is a vertically arranged concentric annulus of 800 mm long and 10 mm hydraulic diameter. The inner tube, SUS 304 of 400 mm long, 8 mm I.D, and 7 mm O.D., is heated uniformly by the low voltage AC power. The wall temperature measurements were performed at the axial distance from the inlet of the heating tube, z=390 mm. 6 chromel- alumel thermocouples of 76 .mu.m were press fitted to the inner surface of the heating tube periphery. To investigate the heat transfer characteristics during the fast transient cooling process, the outer surface (fluid side) temperature and the surface heat flux are computed from the measured inner surface temperature history by means of a numerical method for inverse problems of transient heat conduction. Present cooling (boiling) curve is sufficiently compared with the previous results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.10
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• pp.729-736
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• 2009

Pool boiling heat transfer and critical heat flux (CHF) of water-based nanofluids with alumina and titania nanoparticles of 0.01% by volume were investigated on a disk heater at saturated and atmospheric conditions. The experimental results showed that the boiling in nanofluids caused the considerable increase in CHF on the flat surface heater. It was revealed by visualization of the heater surface subsequent to the boiling experiments that a major amount of nanoparticles deposited on the surface during the boiling process. Pool boiling of pure water on the surface modified by such nanoparticle deposition resulted in the same CHF increases as what boiling nanofluids, thus suggesting the CHF enhancement in nanofluids was an effect of the surface modification through the nanoparticle deposition during nanofluid boiling. Possible reasons for CHF enhancement in pool boiling of nanofluids are discussed with surface property changes caused by the nanoparticle deposition.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.195-204
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• 2011

The effects on pool boiling heat transfer of aqueous solutions of boric acid ($H_3BO_3$) and sodium chloride (NaCl) as working fluids have been studied. Borated and NaCl water were prepared by dissolving 0.5~5% volume concentration of boric acid and NaCl in distilled-deionized water. The pool boiling tests were conducted using $1{\times}1\;cm^2$ flat heaters at 1 atm. The critical heat flux (CHF) dramatically increased compared to boiling pure water. At the end of boiling tests it was observed that particles of boric acid and NaCl had deposited and formed a coating on the heater surface. The CHF enhancement and surface modification during boiling tests were very similar to those obtained from boiling with nanofluids. Additional experiments were carried out to investigate the reliability of the additives deposition in pure water. The boric acid and NaCl coatings disappeared after repeated boiling tests on the same surface due to the soluble nature of the coatings, thus CHF enhancement no longer existed. These results demonstrate that not only insoluble nanoparticles but also soluble salts can be deposited during boiling process and the deposited layer is solely responsible for significant CHF enhancement.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.2
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• pp.20-26
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• 1995

The very rapid cooling problem from $820^{\circ}$C to $20^{\circ}$C on the surface of the steel by thermal conduction including the latent heat of phase transformation of steel and by transient boiling heat transfer of water are considered to principal problem in quenching. The transient boiling process of water at the surface of specimen during the quenching process were experimentally analyzed. Then the heat flux was numerically calculated by the numerical method of inverse heat condition problem. In this report, the simulation program to calculate the cooling curves for large rolls was made using the subcooled transient boiling curve as a boundary condition. By this simulation program, the cooling curves of rolls from D=50mm to D=200mm were calculated and the effects of agitation of circulation of water also investigated.