• Journal of the East Asian Society of Dietary Life
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• v.24 no.2
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• pp.242-251
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• 2014

The traditional food - jungkwa of Korea, is difficult to manufacture. In this study, jungkwa with carrots was made in a rice cooker to simplify preparation. The boiling times for red color, chewiness and overall acceptability of jungkwa with carrots in a rice cooker as compared to the traditional method were 135 minutes, 150 minutes, 165 minutes, 180 minutes and 195 minutes, respectively. The rice cooker produced a lower moisture content in jungkwa with carrots when cooked for a longer time period, whereas the sugar content increased significantly. The color value of jungkwa with carrots was reduced at a longer boiling time as compared to the traditional method, yellowness increased when boiling time was longer than 195 minutes, whereas it remained the same with the traditional method. The hardness of jungkwa with carrots increased and candied jungkwa's result increased significantly when the boiling time was longer than 165 minutes. The rice cooker created a similar chewiness even when boiling time was over 165 minutes, although not consistently. The sensory evaluation scores of jungkwa made with carrots in terms of appearance, smell, taste, texture and overall preference were highest at 150 minutes and 165 minutes. Boiling jungkwa for 150 minutes in the rice cooker is the traditional method which simmers jungkwa at a lower timethan the preference time. Therefore, the best time for boiling jungkwa in the rice cooker highest was 165 minutes. After storage for 15 days chewiness and moisture content of jungkwa made with carrots at different boiling times, increased and decreases respectively. Therefore, the rice cooker can used to achieve comparable jungkwa without the traditional method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.247-255
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• 2004

The cooling characteristic of water-air mixed spray for high water mass flux is not well defined, compared to that of highly pressurized spray. A series of research program was planned to develop the boiling correlation for whole temperature range in case of water-air mixed spray with high water mass flux. The cooling experiments of hot steel surface with initial temperature of 820$^{\circ}C$ were conducted in unsteady state with relatively high water mass flux. A computer program was developed to calculate the heat flux inversely from measured data by three inserted thermocouples. Finally the effects of water and air mass flux on the averaged film boiling heat flux and wetting temperature were studied. In this 1st report, it is found that the boiling curve was similar to that of highly pressurized spray and the decreased slope of heat flux in film boiling region with respect to surface temperature became steep by increasing air mass flux. Also it is shown that, by increasing air mass flux, the averaged heat flux in film boiling region was increased, and then saturated and the wetting temperature was increased, and then decreased. Finally when the heat flux in film boiling region is compared with that of highly pressurized spray, it is known that the cooling is improved by introducing air up to 60%.

• Journal of Energy Engineering
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• v.15 no.1 s.45
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• pp.35-44
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• 2006

This study experimentally investigates effect of boiling heat transfer when ultrasonic vibration was applied. Under the wall temperature condition, temperature distribution in a cavity was measured during the boiling process and heat transfer coefficient of convection, sub-tooled boiling and saturated boiling states were measured with and without ultrasonic vibration, respectively. Also, the profiles of the pressure distribution in acoustic field measured by a hydrophone were compared with the augmentation ratios of heat transfer calculated by local heat transfer coefficient. Result of this study, heat transfer coefficient and augmentation ratio of heat transfer is higher with ultrasonic waves than without one. Especially, augmentation ratio of heat transfer is more increased the convection state than sub-cooled boiling and saturated boiling states. Acoustic pressure is relatively higher near ultrasonic transducer than other points where is no installed it and affects the augmentation ratio of heat transfer.

• Journal of Applied Tourism Food and Beverage Management and Research
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• v.11
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• pp.107-120
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• 2000

무, 당근 및 감자를 대상으로 조리방법 (boiling, pressure cooking, microwave cooking)에 따른 dietary fiber 성분, 수분함량 및 조직감의 변화에 대하여 조사하였으며 조직감에 영향을 미치는 성분에 대해 연구해보았다. 시료내에 존재하는 pectin의 함량은 조리시 원료시료에 비해 현저하게 감소하였으며, microwave cooking>pressure cooking>boiling의 순서로 점차 감소하였다(P<0.05). ADF, NDF 및 Cellulose, Hemicellulose, Lignin은 boiling과 pressure cooking의 경우에는 원료시료에 비해 모든 성분이 증가현상을 나타내었으며, microwave cooking의 경우에는 감소하였다(P<0.01). Hemicellulose와 lignin은 조리에 의한 영향을 거의 받지 않는 것으로 나타났으며, cellulose는 조리 방법에 따라 상당한 영향을 받는 것으로 나타났다. 조리방법에 따른 수분함량의 변화는, boiling시에는 원료시료에 비해 현저한 증가를 보였으며, pressure cooking의 경우에는 조금 감소하였으나 뚜렷한 차이가 없었고, microwave cooking시에는 현저한 감소현상을 나타내었다(P<0.001). 조리 방법에 따른 조직감의 변화는 침투시험시에는 maximum force가 raw>microwave cooking>pressure cooking>boiling의 순서로 점차 감소하였으며, 절단 시험시에는 maximum force가 microwave cooking>pressure cooking>raw>boiling의 순서로 점차 감소하였다. 관능검사 결과, 견고성은 원료시료가 가장 컸으며, microwave cooking>pressure cooking>boiling한 시료의 순서로 점차 감소하였고 씹힘성은 microwave cooking방법으로 조리한 시료가 가장 컸으며, pressure cooking>raw>boiling의 순서로 점차 감소하였다. 기계적 측정 결과와 관능검사 결과를 연관시킨 결과, 높은 연관성이 있었다. 이러한 결과로부터 조리시 시료의 견고성은 pectin의 함량과 밀접한 관계가 있어서, 즉 pectin의 함량이 증가함에 따라 견고성이 증가되는 것을 알 수 있었고, 씹힘성은 수분함량과 밀접한 관련이 있어서, 즉 수분함량이 감소함에 따라 씹힘성이 증가되는 것을 알 수 있다. 이상과 같은 결과들은 무, 당근 및 감자에 있어서 모두 같은 경향을 나타내었다.

• 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 the Korean Solar Energy Society
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• v.29 no.5
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• pp.35-44
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• 2009

In this study, boiling heat transfer coefficients(HTCs) and critical heat flux(CHF) are measured on a smooth square flat copper heater in a pool of pure water with and without carbon nano tubes(CNTs) dispersed at $60^{\circ}C$. Tested aqueous nanofluids are prepared using multi-walled CNTs whose volume concentrations are 0.0001, 0.001, 0.01, and 0.05%. For dispersion of CNTs, polyvinyl pyrrolidone(PVP) is used in distilled water. Pool boiling HTCs are taken from $10kW/m^2$ to critical heat flux for all nanofluids. Test results show that the pool boiling HTCs of the nanofluids are lower than those of pure water in entire nucleate boiling regime. On the other hand, critical heat flux is enhanced greatly showing up to 200% increase at volume concentration of 0.001% CNTs as compared to that of pure water. This is related to the change of surface characteristics by the deposition of CNTs. This deposition makes a thin CNT layer on the surface and the active nucleation sites of heat transfer surface are decreased due to this layer. The thin layer acts as the thermal resistance and also decreases the bubble generation rate resulting in a decrease in pool boiling HTCs. The same layer, however, maintains the nucleate boiling even at very high heat fluxes and reduces the formation of large vapor canopy at near CHF resulting in a significant increase in CHF.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.4
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• pp.365-379
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• 1994

Pool boiling experiments were carried out to study the effect of electric field on nucleate boiling heat transfer. CFC-11 and its alternative HCFC-123 were used as working fluids. Boiling on both single tube and a bundle of five tubes was investigated. Heat flux varied from 5 to $25kW/m^2$ while the applied voltage changed from 0 to 1kV. The results showed that at low heat flux where boiling was not present or very weak, electric field-induced forced convection helped increase the heat transfer coefficients of CFC-11 and HCFC-123 significantly(4-15 times increase). However, at higher heat flux, nucleate boiling of CFC-11 which is a highly dielectric fluid, was not affected significantly by the application of electric field. In contrast to CFC-11, even at high heat flux, nucleate boiling of CFC-11 which has a relatively larger electric conductivity than CFC-11, was vigorously increased up to 2-4 times. The additional power required to apply the electric field was 1-2% of the total power consumption by the heater. The increase in overall heat transfer coefficient of evaporators with HCFC -123 was about 40%, suggesting a considerable reduction in evaporator size with EHD technique.

• The Korean Journal of Food And Nutrition
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• v.13 no.6
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• pp.529-533
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• 2000

The marsh calm soup was prepared with 2 volumes of boiling water and heated for 0, 5, 10, 30, 60 and 120 minutes. As the boiling time prolonged, water content decreased gradually, while protein content increased. Free amino acid content was the highest with 30 minutes of boiling showing 103.1 mg/100g, and decrease showly thereafter. Among the free amino acids, alanine was the most abundant followed by proline, glutamic acid and glycine. Degree of protein hydrolysis increased as boiling prolonged. In the non-volatile organic acids, succinic acid was the highest(137.08 mg/100g with 30 minutes of boiling), followed by oxalic acid, magic acid and lactic acid. The optimum boiling time for marsh calm soup was evaluated to be 30 minutes.

• Journal of the Korean Chemical Society
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• v.59 no.4
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• pp.289-295
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• 2015

The purpose of this study was to survey the elementary school teachers' thoughts of the classification criteria for evaporation and boiling concept in the heating and non-heating conditions. For this purpose, we conducted a survey and interviews with 37 elementary school teachers. When the heating conditions were presented, many teachers thought evaporation phenomena as boiling. In opposite condition, many teachers thought boiling phenomena as evaporation. This means that teachers‘ thought of boiling phenomena was connected with heating conditions and evaporation phenomena with non-heating conditions. In addition, the classification criteria to distinguish evaporation and boiling phenomena depending on the heating and non-heating conditions were not coherent. In this study, we suggested that a various cases beyond the typical case must be presented in the textbooks and teaching in order to avoid confusion of thoughts related to evaporation and boiling concepts.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.87-88
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• 2010