• Journal of the Korean Society of Visualization
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• v.18 no.3
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• pp.23-34
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• 2020

Two-phase flow and heat transfer characteristics during the reflood phase of a single heated rod in the KHU reflood experimental facility were examined. Two-phase flow behavior during the reflooding experiment was carefully visualized along with transient temperature measurement at a point inside the heated rod. By numerically solving one-dimensional inverse heat conduction equation using the measured temperature data, time-resolved wall heat flux and temperature histories at the interface of the heated rod and coolant were obtained. Once water coolant was injected into the test section from the bottom to reflood the heated rod of >700℃, vast vapor bubbles and droplets were generated near the reflood front and dispersed flow film boiling consisted of continuous vapor flow and tiny liquid droplets appeared in the upper part. Following the dispersed flow film boiling, inverted annular/slug/churn flow film boiling regimes were sequentially observed and the wall temperature gradually decreased. When so-called minimum film boiling temperature reached, the stable vapor film between the heated rod and coolant was suddenly collapsed, resulting in the quenching transition from film boiling into nucleate boiling. The moving speed of the quench front measured in the present study showed a good agreement with prediction by a correlation in literature. The obtained results revealed that typical two-phase flow and heat transfer behaviors during the reflood phase of overheated fuel rods in light water nuclear reactors are well reproduced in the KHU facility. Thus, the verified reflood experimental facility can be used to explore the effects of other affecting parameters, such as CRUD, on the reflood heat transfer behaviors in practical nuclear reactors.

• Korean journal of food and cookery science
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• v.30 no.6
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• pp.670-678
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• 2014

The purpose of this study was to find the optimal swelling method and condition for seacucumber to improve its taste and texture to accomodate the rapid increase of consumption. Another purpose was to try to determine an easy way to soak dried sea-cucumber under different conditions, and identify the influence of swelling time on the texture of sea-cucumber, in order to reduce preparation time and provide basic data for easy handling. After boiling or steaming for six different periods including 5, 15, 30 and 60 minutes the texture of the sea-cucumbers were compared, For the additive test, the sea-cucumbers were boiling for 30 minutes period with 4 different additives and the textures were compared, Since the texture is an important characteristic of sea-cucumber, there are many variables that affect this property including the, drying and preservation methods. This study provides basic understanding of the influence of the heating method, time and temperature on the swelling of sea-cucumber for handy use at processing sites.

• Journal of the East Asian Society of Dietary Life
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• v.10 no.3
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• pp.239-244
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• 2000

Effects of acetic acid, malic acid and citric acid on copper dissolution from new and used copper saucepans at different concentrations (0, 0.02. 0.04, 0.1 0.2, 0.4, 1.0, 2.0, 4.0%), different boiling times (0,10, 20. 30, 40, 50, 60mins.), and different temperatures (5, 20, 40, 60, 80, 10$0^{\circ}C$ ) were investigated. As acetic acid concentration increases, copper content increases. Copper dissolution concentration from copper saucepans at boiling in malic acid increases more than in acetic acid or citric acid. At above 6$0^{\circ}C$, as the temperature increases, the concentration of copper dissolved from copper saucepans also increases. As boiling time increases, the concentration of copper dissolved from copper saucepans also increases. In addition, through repeated use, the concentration of copper increases as well. And copper concentration dissolves in large amounts from used saucepans rather than new saucepans. The dissolution of copper with distilled water by repeated use does not dissolve at all. 1% acetic acid dissolves in large quantities.

• Journal of ILASS-Korea
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• v.20 no.4
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• pp.236-240
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• 2015

This study aims to experimentally investigate the evaporation characteristics of nanofluid droplet on heated surface at boiling temperature of DI-water. In particular, textured surface was used to examine the effect of wettability on evaporation. At the initial stage of evaporation process, dynamic contact angle (DCA) of nanofluid droplet with 0.01 vol.% concentration on textured surface rapidly increased over its equilibrium contact angle by generated large bubble inside the droplet due to lower wettability. However, contact angle of nanofluid droplet with higher concentration on textured surface decreased with surface tension. In addition, total evaporation time of droplet on textured surface was considerably delayed due to reduction of contact area between droplet and solid surface. Thus, evaporation characteristics were highly affected by the nanofluid concentration and surface wettability.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.15-21
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• 2003

The liquid phase LPG injection engine is a new technology to make good use of LPG as a clean energy. However, it is difficult to precisely control air/fuel ratio in the system because of variation of fuel composition, change of temperature and flash boiling injection mechanism. This study newly suggests an injector control logic for liquid phase LPG injection systems. This logic compensates a number of effects such as variations of density, stoichiometric air/fuel ratio, injection delay time, injection pressure, release pressure which is formed by flash boiling of fuel at nozzle exit. This logic can precisely control air/fuel ratio with only two parameters of intake air flow rate and injection pressure without considering fuel composition, fuel temperature.

• Journal of the Korean Wood Science and Technology
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• v.25 no.3
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• pp.8-15
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• 1997

The ultrasonic velocity and dynamic MOE of acetylated bamboos were investigated using PUNDIT, a transit time measuring device for longitudinal ultrasonic propagation. Bamboo specimens were boiled in acetic anhydride for 2, 4 and 6 hours, and the maximum average WPG (Weight Percentage Gain) of 19% was obtained at 6 hours. The volumes of acetylated bamboos increase with boiling time and WPG, while as WPG increases their oven-dry densities generally increase with a concave around 5% WPG. This oven-dry density pattern likely influences the trends of ultrasonic velocity and dynamic MOE. which generally decrease with a convex around 5% WPG. It is postulated that during boiling extractives in a bamboo move and aggregate at its surfaces transiently, resulting in the increase of ultrasonic velocity and dynamic MOE. To explain the fact that ultrasonic velocity varies with WPG a simple model was proposed and some ultrasonic properties of a transmitted wave were examined.

• Journal of the Korean Society of Food Science and Nutrition
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• v.3 no.1
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• pp.13-16
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• 1974

The change in color of vegetables containing chlorophyll on cooking has been of concern to food scientists. This experiment was initiated to determine the effect of different heating methods and time on the chlorophyll of green pepper. Peppers were heated at 100 C for 5, 10, and 15 min by using boiling water, steam and hot air and for 1, 2 and 3 min in microwave oven. The results showed that chlorophyll content decreased with increasing heating time. Among the heat treatments employed steaming gave the greatest effect and boiling water was the next. Hot air and microwave treated samples changed only small amount of chlorophyll. Generally pheophytin formation was increased with decreasing chlorophyll content.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.5 s.236
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• pp.643-652
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• 2005

Saturated nucleate pool boiling experiments for binary mixtures, which are consisted of refrigerant R11 and R113, were performed with constant wall temperature condition. Results for binary mixtures were also compared with pure fluids. A microscale heater array and Wheatstone bridge circuits were used to maintain the constant temperature of the heating surface and to obtain heat flow rate measurements with high temporal and spatial resolutions. Bubble growth images were captured using a high speed CCD camera synchronized with the heat flow rate measurements. The departure time for binary mixtures was longer than that for pure fluids, and binary mixtures had a higher onset of nucleate boiling (ONB) temperature than pure fluids. In the asymptotic growth region, the bubble growth rate was proportional to a value between $t^{\frac{1}{6}}$ and $t^{\frac{1}{4}}$. The bubble growth behavior was analyzed to permit comparisons with binary mixtures and pure fluids at the same scale using dimensionless parameters. There was no discernable difference in the bubble growth behavior between binary mixtures and pure fluids for a given ONB temperature. And the departure radius and time were well predicted within a ${\pm}30{\%}$ error. The minimum heat transfer coefficient of binary mixtures occurred near the maximum ${\mid}y-x{\mid}$ value, and the average required heat flux during bubble growth did not depend on the mass fraction of R11 as more volatile component in binary mixtures. Finally, the results showed that for binary mixtures, a higher ONB temperature had the greatest effect on reducing the heat transfer coefficient.

• Korean journal of food and cookery science
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• v.6 no.3 s.12
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• pp.17-24
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• 1990

1. The major components of Omija were found as moisture (16.12%) crude fat (10.5%) crude protein (8.66%) crude ash (3.47%) reducing sugar (5.32%). 2. Omija jelly receipe were summarized as follow; (1) 5% of gelatin concentration was shown to be the most desirable. (2) 15% of sugar concentration was shown to be the most desirable. (3) 12, 15, 18 hrs. of extract time was not significantly different in Omija extract. (4) It was the most desirable for 30g of Omija to boil during 30 minutes in boiling Omija extract. 3. Result of Omija jelly by Instron that Hardness, Adhesiveness, Gumminess tend to increase as the addition level of gelatin concentration increased but Cohesiveness was changed irregularly. 4. Hardness Adhesiveness tend to increase as the addition level of increase as the addition level of sugar concentration increased but Cohesiveness Gumminess was not significant difference. 5. Hardness, Adhesiveness tend to increase as the addition level of extract time increased, but Cohesiveness, Gumminess was not significant difference. 6. Color value of Omija jelly (gelatin 5%, sugar 15%, 18hr. extract) was shown $x=7.94{\pm}0.047,\;y=4.24{\pm}0.047,\;z=6.34{\pm}0.067$ in Omija extract and Omija jelly (gelatin 5%, sugar 15%, Omija 50g, 30 minutes boiling) was shown $x=7.76{\pm}0.038,\;y=3.88{\pm}0.02,\;z=6.12{\pm}0.021$ in boiling Omija extract. 7. Appearance of Omija jelly had significant relationship with Cohesiveness by gelatin concentration and texture of Omija jelly had significant relationship with Adhesiveness by gelatin concentration. 8. Appearance of Omija jelly had significant relationship with Cohesiveness and texture of Omija jelly had significant relationship with Gumminess by boiling Omija extract.

• Korean journal of food and cookery science
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• v.15 no.5
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• pp.490-499
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• 1999

The purpose of this study was to investigate the changes of taste components in the boiled beef brisket soup stock and shank soup stock by varying pretreatment, boiling temperature and time. Free amino acids and nucleotides color and sensory evaluation in each samples were analyzed. The results were obtained as follows : 1. The amount of free amino acids in the brisket soup stock pretreated by soaking and blanching showed a tendency to increase in proportion to boiling time. The amount of glutamic acid in the brisket soup stock was much in order of soaking > blanching > roasting pretreatment. While the amount of glutamic acid in the boiled soup stock samples pretreated by soaking and blanching was much more at low temperature than at high temperature, the glutamic acid contents in the boiled soup stock pretreated by roasting were large at high temperature. The amount of glutamic acid in pretreated by soaked soup stock showed the highest and recorded 8.73 mg% at 6 hour-low temperature-boiling. 2. The amount of free amino acids in the shank soup stock did not show any regular tendency and had few changes in quantity by the methods of pretreatment. Each amount of glutamic acid in the shank soup stock pretreated by soaking and blanching was the highest, when boiled for 3 hours at high temperature. The samples pretreated by roasting showed the highest record 2.49 mg%, when boiled for 6 hours at high temperature, but could not recognize any regular tendency in the case of boiling at low temperature. 3. The amount of nucleotides in the brisket soup stock generally showed increase in proportion to boiling time. The amount of 5'-IMP extracted from the brisket soup stock was much in order of blanching > soaking > roaking pretreatment, but few differences between blanching and soaking soup stock samples. The amount of 5'-IMP extracted from soup stock samples pretreated by soaking and blanching was high at low-boiling and by roasting at high-boiling. Each amount of 5'-IMP extracted from soup stocks pretreated by soaking(BSL) and blanching(BBL) was the highest at 6 hour-low-boiling(37.06 mg%), and 5 hours(38.37 mg%) respectively. The amount of 5'in the soup stock pretreated by roasting(BRH) showed the highest records at 6 hour-high-boiling(10.85 mg%). 4. The amount of 5'-IMP extracted from the shank soup stock preteated by soaking and blanching showed a tendency to decrease after 3 hours boiling irrelative of boiling temperature. The amount of 5'in the shank soup stock was much in order of soaking > blanching > roasting pretreatment and showed high at the boiling of high temperature. In the sample pretreated by roasting it showed the highst records when boiled for 6 hours at high temperature(1.55 mg%). 5. The L Value of the brisket soup stock pretreared by roasting at high temperature(BRH) was the lowest and the b value of it was the highest of all the brisket samples boiled for 6 hours. No differences were found in the Value of L, a, and b in shank soup stock by the methods of pretreatment and boiling temperature. 6. The sensory scores in color and flavor of the brisket soup stock showd that BRH was higher than the other samples, and the preference in taste and overall was the highest in BSH while it was the lowest in BRH. The preference in the all sensory characteristics of SSH was higher than any other shank soup stock, but did not show any significant difference statistically.