• 대한기계학회논문집B
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• 제21권12호
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• pp.1563-1575
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• 1997

To understand EHD nucleate boiling heat transfer enhancement, EHD effects on R-113 nucleate boiling heat transfer in a non-uniform electric field were investigated. The pool boiling heat transfer and the dynamic behavior of bubbles in d.c./a.c. electric fields under a saturated or subcooled boiling were studied by using a plate-wire electrode and a high speed camera. From the pool boiling heat transfer study, the shift of the pool boiling curve, the increase of the heat transfer and the delay of ONB and CHF points to higher heat fluxes were observed. From the dynamic behavior of bubbles, it was observed that bubbles departed away from the whole surface of the heated wire in radial direction due to EHD effects by a nonuniform electric field. With increasing applied voltages, the bubble size decreased and the active nucleation site and the departure number of bubbles showed the different trend. The present study indicates that the EHD nucleate boiling heat transfer is closely connection with the dynamic behavior of bubbles and the secondary flow induced near the heated surface. Therefore, the basic studies on the bubble behavior such as bubble frequency, bubble diameter, bubble velocity and flow characteristics are necessary for complete understanding of the enhancement mechanism of the boiling heat transfer using an electric field.

• Journal of Advanced Marine Engineering and Technology
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• 제38권5호
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• pp.581-588
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• 2014

Extensive researches toward pool boiling characteristics have been widely investigated. However, the correct understanding of its boiling crisis by Critical Heat Flux (CHF) phenomenon during steady and transient heat transfer as a fundamental database for designing heat generation systems is still need to be clarified. The pool boiling CHFs were investigated to clarify the generalized phenomena of transition to film boiling at transient condition. The CHFs were measured on 1.0 mm diameter horizontal cylinder of platinum for exponential heat generation rates with various periods for saturated liquids at atmospheric pressure. The incipience of boiling processes was completely different depending on pre-pressurization. Also, the dependence of pre-pressure in transient CHFs changed due to the wettability of boiling liquids. The trend of typical CHFs were clearly divided into the first, second and third groups for long, short and intermediate periods, respectively. By the effect of pre-pressurization, the boiling incipience mechanism was replaced from that by active cavities entraining vapor to that by the HSN in originally flooded cavies.

• Nuclear Engineering and Technology
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• 제43권3호
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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.

• 한국식품조리과학회지
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• 제1권1호
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• pp.40-44
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• 1985

The change of PH, texture, swelling$.$power and protein, fat, calorie composition at cooking rice boiling with various cereal were summarized as follows : 1. The change in pH resulting from the addition of various cereal were much more pronounced in boiling rice with cereal than boiling rice. 2. The volume of boiling rice with cereal was higher that the addition of various cereal. 3. The evaluation of the texture of boiling rice with cereal was the most that rice 70％, barly, bean, red-bean each 10％ composition.

• 한국식품저장유통학회지
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• 제4권3호
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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.

• 동아시아식생활학회지
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• 제14권4호
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• pp.387-396
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• 2004

It was investigated to study the sensory and physicochemical properties of chicken consomme made with different boiling time(1, 2, 3, and 4 hr). The sensory properties were evaluated with respect to both the acceptability (color, smell, mouthfeel, taste, overall acceptability) and intensity characteristics (color, smell, clarify, taste). From the results, the 3hr treatment was most favored for smell, mouthfeel, taste and overall acceptability, from the sensory evaluation tests. According to a quantitative descriptive analysis of the sensory evaluation for the treatments, the color and smell showed higher scores by increasing the boiling time. Whereas, in clarify and taste, the 3hr treatment showed the highest values. As for the physicochemical characteristics, the pH was increased with increasing boiling time. The reducing sugars, turbidity and viscosity increased with increasing boiling time. The colorimetric lightness values L decreased, and redness a, yellowness b and color difference values ΔE increased with increasing boiling time. There were 18 free amino acids indentified ； the glutamic acid, alanine, arginine and lysine were high in the free amino acid of the chicken consomme made with different boiling times. There were 3 free sugar indentified, glucose, fructose and sucrose. The free amino acid and free sugars contents increased with increasing boiling time. There were changes in the mineral contents of the chicken consomme made with different boiling time ; with high K, Na, P, Mg, Ca and Fe contents. The mineral contents increased with increasing boiling time. Especially, the 3hr treatments was more highly increased than rest of the treatments in all characteristics. The results showed the chicken consomme made by boiling far 3hr was the most preferably in the sensory and physicochemical quality.

• 기본간호학회지
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• 제6권1호
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• pp.78-95
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• 1999

The grafting of a kidney has been found to be the best medical treatment for patients who have renal insufficiency failure, but the patients still have experienced much trouble and apprehension. This study was done to further nursing theory developing for patients who have has a kidney graft from another person. The research method followed grounded theory methodology of Strauss and Corbin. The subjects were three female and four male patients. This study done befween Oct. 1997 and Mar. 1998. All of the subjects were interviewed by the author. Interview were done by the long interview technique and observation. In the process of data analysis, 'heart-boiling' was found to be the core phenomenon. The results were composed to 101 concepts. These concepts were grouped into nineteen categories, and then to twelve categories. There were 12 super-class categories as follows ; 'pain', 'heart-boiling', 'experience of dialysis', 'term of admission to a hospital', 'support of other person', 'dependence on God', 'direction', 'negative reaction', 'positive reaction', 'comfortable', 'lacking', 'acceptance'. In this process, 14 hypotheses were derived from the categories as follows ; (1) The more experience with dialysis that the patients have, the stronger the heart-boiling will tend to be. (2) The less experience with dialysis the patients have, the weaker the heart-boiling will tend to be. (3) The longer admission to hospital the patients have, the stronger the heart-boiling will be. (4) The shorter the admission to hospital the patients have, the weaker the heart-boiling will be. (5) The weaker the intense-grief is, the more positive the reaction to heart-boiling the patients wll have. (6) The stronger the intense-grief is, the more negative the reaction to heart-boiling the patients will have. (7) The stronger the support of other persons that the patients have, the more positive the reaction to heart-boiling the patients will have. (8) The weaker the support of other person that the patients have, the more negative the reaction to heart-boiling the patients will have. (9) The stronger the dependence on God that the patients have, the mure positive reaction to heart-boiling the patients will have. (10) The weaker the dependence on God that the patients have, the more negative reaction to heart-boiling the patients will have. (11) The more positive thoughts that the patients have, the more positive reaction to heart-boiling the patinets will have. (12) The more negative thoughts that the patients have, the more negative reaction to heart-boiling the patients will have. (13) The more positive reaction the patients have, the more free from heart-boiling the patients tend to be. (14) The more negative reaction the patients have, the less free from heart-boiling the patients tend to be. From the analysis of observed data and comparing each class, I concluded that there are four formula relation types between reaction of patients and heart-boiling. (1) If patients have the experience of dialysis, have a long term admission to hospital, are strong in heart-boiling, depend on God, have positive thoughts and another's strong support, they experience release by positive reaction to the intense-grief. (2) If patients have the experience of dialysis, have a short term admission to hospital, are weak in heart-boiling, do not depend on God, have negative thoughts, and have few supports from others, they experience attachment to heart-boiling though a negative reaction. (3) If patients have the experience of dialysis, have a long term admission to hospital, are strong in heart-boiling, do not depend on God, and have negative thoughts, they experience attachment to heart-boiling through negative reaction in spite of support from another. (4) If patients have the experience of dialysis, have a long term admission into hospital, are strong in heart-boiling and satisfaction is low, but they have positive thoughts, then they experience acceptance and harmony through the positive reaction to heart-boiling. The results of this study are expected to help the way nurses care for patients who have had a kidney graft from another.

• 대한기계학회논문집B
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• 제27권5호
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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.

• 설비공학논문집
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• 제9권3호
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• pp.276-283
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• 1997

The nucleate boiling heat transfer experiments are performed using a ternary refrigerant R407C which is a candidate of alternatives of HCFC 22. The boiling phenomena for R-32, R-125, and R-134a which are the constituent refrigerants of R407C are also investigated to give the foundation of theoretical research for the mixture component boiling. The nucleate boiling heat transfer coefficients of R407C is less than those of HCFC 22 which has the similar physical and transport properties. Since the experimental results show the deterioration of boiling heat transfer coefficients of ternary mixture refrigerants R407C, the boiling heat transfer coefficients of R407C cannot be obtained by the linear combination of boiling heat transfer coefficients from its constituent components R-32, R125, and R134a.

• 설비공학논문집
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• 제15권4호
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• pp.254-260
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• 2003

The boiling characteristics for R134a are studied to clarify the hysteresis at low temperature on enhanced tubes of a flooded evaporator. Initial boiling conditions, refrigerant temperature, and inlet temperature of the chilled water are considered as the key parameters of the experiments. Unlike previous studies of the boiling heat transfer with uniform heat flux and uniform wall temperature, the wall temperature was varied along the tube. In, this study, it was found that the hysteresis of the temperature overshoot (705) at the onset of nucleate boiling initially at the inlet section of the tube. It is also concluded that the abnormal operation can be avoided during the low temperature boiling if the refrigeration system is started with LMTD larger than $3.4^{\circ}C$ at initial stage and larger than $1.0^{\circ}C$ at normal stage.