• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.86-91
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• 2011

Thermal design was conducted for a solar thermal storage system in a medium-temperature range between $200^{\circ}C$ and $400^{\circ}C$. The system was composed of heat pipes as heat carrier and molten salts as phase-change storage material. Each heat pipe penetrated through the storage system and had two heat-exchanging sections at both ends to interact with high-and low-temperature steams, while it exchanged heat with molten salts in the middle section. During a heat-storage mode, the heat pipes transferred heat from the hot steam at one side to the molten salts and it transferred heat from the molten salt to the cold steam at the other side during the heat-dissipating mode. A tube-bank type heat exchanger theory was applied to this design task to meet the required inlet and outlet temperatures of the steams depending on the operation modes. Several design variables were considered including the lengths of evaporator and condenser of a heat pipe, traverse and longitudinal pitches of the pipe, and the number of rows of the heat pipes for two different molten salt baths. An optimum design results were presented with discussion.

• Journal of the Korean Institute of Gas
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• v.24 no.6
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• pp.61-69
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• 2020

This paper is a study of the behavior characteristics that occur in the hydrogen storage vessel TYPE 1 according to pressure and temperature conditions by FEM(Finite element method). Von Mises stress (VMS) generated at the highest pressure was compared with Yield strength (YS) of the material for structural safety assessment of the container, and the results of plastic strain energy density (PSED) were analyzed as basic data for life expectancy. According to the analysis results, the safety of the hydrogen gas storage vessel is not ensured due to the occurrence of VMS higher than the yield strength on the bottom of the storage container at a gas pressure of 40 Mpa or higher. In addition, the results of VMS caused by temperature conditions are very low and the behavior by temperature can be ignored. The maximum pressure of VMS/YS below 1 is calculated to be about 30 Mpa, indicating that the hydrogen storage container subject to this paper should be managed with a gas charging pressure of less than 30 Mpa.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.193-197
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• 2006

The sodium/sulfur(Na/S) battery has many advantages such as high theoretical specific energy(760Wh/kg), and low material cost based on the abundance of electrode material in the earth. It has been reported that the electrochemical properties of sodium/sulfur cell above $300^{\circ}C$, utilized a solid ceramic electrolyte and liquid sodium and sulfur electrodes. A lot of researches have been performed in this field. Recently, Na/S battery system was applied for electricity storage system for load-leveling. One of severe problems of sodium/sulfur battery was high operating temperature above $300^{\circ}C$, which could induce the explosion and corrosion by molten sodium, sulfur and polysulfides. In order to develop sodium battery operated at low temperature, sodium ion battery has been studied using carbon anode, and sodium oxides cathodes. However, the energy densities of the sodium ion batteries were much lower than high temperature sodium/sulfur cell. In this study, the sodium/sulfur battery with 1M $NaCF_3SO_3$ is tested at room temperature. The charge-discharge mechanism was discussed based on XRD, DSC, SEM and EDS results.

• Food Science and Preservation
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• v.14 no.3
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• pp.227-232
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• 2007

The development of an effective long-term storage protocol for harvested fresh pepper is urgently required to increase the market for pepper products. The protocol must minimize quality loss, so that the product may be used either as a spice or as a raw material for processed pepper products, both in the home and in food processing plants. We investigated the optimum size of pepper fruits, freezing temperatures, storage periods, and thawing methods, to establish an optimum storage protocol. This study was conducted not only to develop freezing and thawing methods for long term storage of harvested red pepper, but also to develop processed pepper products utilizing the stored pepper. We aimed to expand the pepper products market and to increase the incomes of pepper growers. Whole red pepper, sliced red pepper, and crushed red pepper were frozen and stored at $-5^{\circ}C,\;-20^{\circ}C,\;or\;-40^{\circ}C$. The soluble solid content and the vitamin C level showed maximal stability at $-40^{\circ}C$, although total free sugars decreased on storage at all temperatures tested. Such Changes were more marked at $-5^{\circ}C$ than at the other(lower) temperature tested. The vitamin C content of whole red pepper was higher than that of sliced red pepper or crushed red pepper. Room-temperature thawing resulted in twice the drip loss seen on low temperature($5^{\circ}C$) thawing or microwave oven thawing. Brown discoloration was a serious problem with room temperature thawing. Total free sugars were higher in samples thawed at low temperature or in the microwave oven, compared to the level seen after room-temperature thawing. pepper samples thawed at low temperature scored higher in sensory tests than samples thawed at room temperature.

• Solar Energy
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• v.8 no.1
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• pp.13-21
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• 1988

Heat transfer phenomena in a high-temperature heat storage unit were investigated using molten salts. Carbonate salt, an equimolar mixture of $Li_2CO_3$ and $K_2CO_3$, which melts at $505^{\circ}C$ with a latent heat of 82 cal/g, was selected as the most promising latent heat storage material based on its low cost and excellent thermophysical properties at moderately high temperatures. It was also found that nitrate salts were good candidates of sensible heat storage materials. For the carbonate salt to be utilized commercially, however, several means of enhancing thermal recovery must be explored by promoting heat conduction through the solid salt formed during the heat discharge period. These would be achieved by the additions of aluminum screens and wool, and stainless fins. Finally, experimental results of moving boundary of phase change were well compared with predictied values obtained from the approximate solution.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.962-971
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• 2004

This paper has dealt with thermo-physical properties of microencapsulated phase change material slurry as a latent heat storage material having a low melting point. The measured results of the thermo-physical properties of the test microencapsulated phase change material slurry, those are, density, specific heat, thermal conductivity and viscosity, were discussed for the temperature region of solid and liquid phases of the dispersion material (paraffin). The measurements of these properties of microencapsulated phase change material slurry have been carried out by using a specific-gravity meter, a water calorimeter, a differential scanning calorimeter(DSC), a transient hot wire method and rotating type viscometer, respectively. It was clarified that the additional properties law could be applied to the estimation of the density and specific heat of microencapsulated phase change material slurry and also the Euckens equation could be applied to the estimation of the thermal conductivity of this slurry.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.6
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• pp.499-505
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• 2004

The objective of this study is to investigate the effect of supercooling repression on the TMA clathrate by adding ethylene glycol. For this purpose, phase change temperature, supercooling, specific heat, latent heat and rate of volume change were measured and evaluated experimentally for heat source temperatures of -6$^{\circ}C$, -7$^{\circ}C$, -8$^{\circ}C$. The results show that supercooling was decreased. Thus the experimental results are expected to be used for the increase of coefficient of performance of low temperature thermal storage system in the building.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.2
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• pp.178-183
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• 2011

Metal hydride alloys are a promising type of material in hydrogen storage applications, allowing for low-pressure, high-density storage. However, while many studies are being performed on enhancing the hydrogen storage properties of such alloys, there has been little research on large-scale storage vessels which make use of the alloys. In particular, large-scale, high-density storage devices must make allowances for the inevitable generation or absorption of heat during use, which may negatively impact functioning properties of the alloys. In this study, we develop a numerical model of the discharge properties of a high-density MH hydrogen storage device. Discharge behavior for a pilot system is observed in terms of temperature and hydrogen flow rates. These results are then used to build a numerical model and verify its calculated predictions. The proposed model may be applied to scaled-up applications of the device, as well as for analyses to enhance future device designs.

• Korean Journal of Food Science and Technology
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• v.19 no.2
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• pp.176-180
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• 1987

The sorption characteristics of dried garlic flakes stored at various relative humidity and storage temperature were studied. At low relative humidity below RH 51%, the sorption equilibrium was easily attained, whereas at higher relative humidity above RH 67%, the flakes were browned by higher equilibrium moisture content. The flakes were browned at relative humidity above 67% at $20^{\circ}C$ and $35^{\circ}C$, above 84% at $5^{\circ}C$, respectively. The moisture contents of monolayer value for the flakes were ranging from 5.80% to 6.20% (DB) with varying temperatures. And the necessity of moisture-proof packaging material suggested for the long term storage of the flakes because the lower moisture content and storage temperature, the higher driving force of wetting. Regression equation for browning rate prediction with relative humidity and storage temperature of the flakes was determined.

• Nuclear Engineering and Technology
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• v.42 no.3
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• pp.249-258
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• 2010

Recently, many utilities have considered interim dry storage of spent nuclear fuel as an option for increasing spent fuel storage capacity. Foreign nuclear regulatory committees have provided some regulatory and licensing requirements for relatively low- and medium-burned spent fuel with respect to the prevention of spent fuel degradation during transportation and interim dry storage. In the present study, the effect of cladding creep and hydride distribution on spent fuel degradation is reviewed and performance tests with high-burned Zircaloy-4 and advanced Zr alloy spent fuel are proposed to investigate the effect of burnup and cladding materials on the current regulatory and licensing requirements. Creep tests were also performed to investigate the effect of temperature and tensile hoop stress on hydride reorientation and subsequently to examine the temperature and stress limits against cladding material failure. It is found that the spent fuel failure is mainly caused by cladding creep rupture combined with mechanical strength degradation and hydride reorientation. Hydride reorientation from the circumferential to radial direction may reduce the critical stress intensity that accelerates radial crack propagation. The results of cladding creep tests at $400^{\circ}C$ and 130MPa hoop stress performed in this study indicate that hydride reorientation may occur between 2.6% to 7.0% strain in tube diameter with a hydrogen content range of 40-120ppm. Therefore, it is concluded that hydride re-orientation behaviour is strongly correlated with the cladding creep-induced strain, which varies as functions of temperature and stress acting on the cladding.