• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.133-135
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• 2003

Cryogenic systems are requirement for the operation of HTS power cables. In general, HTS power cables require temperature below 77K, a temperature that can be achieved from the liquid nitrogen at latm or sub-cooled LN2 above latm. HTS power cable needs sufficient refrigeration to overcome its low temperature heat loading. This loading typically cones in two forms : (1) heat leaks from the surroundings and (2) internal heat generation. This paper explains the cooling test system of 10m HTS power cable. This system is composed of storage dewar, auto fill system, core cryostat and cold-box. Storage dewar is a LN2 storage tank and auto fill system is a LN2 supply device to the sub-cooler, Core cryostat is a LN2 flow line. Cold box is a control unit of temperature and flow rate. It is composed of control valve, flow meter, sub-cooler and circulation pump, etc..

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1261-1266
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• 2008

Experimental study was performed to understand the operations of a showcase working in a discount store. Temperatures of evaporation, condenser were measured and also electric power consumption of compressor were measured. The purpose of this study is to application use of cold-heat storage systems operated the showcase. At the condition using ice storage system, the ice making process was operated during midnight being not needed the cooling of the showcase through the continuous running of the condenser unit. And then, the refrigerant was sub-cooled using stored cold-heat after being discharged from the air cooling condenser during the day time. The cooling performance was increased owing to the sub-cooling of refrigerant during day time, hence the running time of the compressor was effectively decreased. In other words, this study showed that power consumption during daytime can be transferred to the midnight for making use of the refrigerant sub-cooling. So the operating characteristics of the showcase system under various working conditions were analyzed and discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.6
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• pp.503-511
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• 2002

Heat flow characteristics during hot water extraction process was studied experimentally. Data were taken at various outlet port type for the fixed inlet port type, inlet-outlet temperature differences and mass flow rates. In this study, the temperature distribution in a storage tank and an outlet temperature were measured to predict a degree of stratification in the storage tank, and a useful rate of hot water was analysed with respect to the variables dominating a extraction process. Experimental results show that the degree of stratification and useful rate of hot water are all high in a low flow rate in case of using modified distributor I (MDI) as the outlet port type.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.6
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• pp.369-374
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• 2010

A refrigerant-subcooling refrigeration system consisted of a typical single vapor-compression refrigeration cycle, a subcooler, and an ice storage tank. The degree of subcooling at the exit of the condenser can be increased by the heat exchange between the subcooler and the ice storage tank. The cold heat in the ice storage tank was stored by using the refrigeration cycle during night time and then used to absorb the heat from the subcooler during daytime. The performance of the refrigerant-subcooling refrigeration system was measured by varying the degree of subcooling. In addition, the performance characteristics of the present system were compared with those of a conventional refrigeration system. The mass flow rate of the present system was higher than that of the conventional system due to the increase in the degree of subcooling. Generally, the refrigerant-subcooling system showed superior performance to the conventional refrigeration system.

• Food Science and Preservation
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• v.20 no.1
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• pp.52-61
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• 2013

This study was conducted not only to investigate the effects of rate of addition of dried jujube to Yakju (0, 0.5, 1.0, 1.5, 2.0 percent) but also to examine the quality changes in jujube Yakju during its storage (for 75 days at $35^{\circ}C$). The results showed no significant differences in pH, total acidity, soluble solids, and anthocyanin and alcohol contents of the Yakju right after its fermentation. With the increase in the amount of jujube that was added, the lightness of the jujube Yakju changed from 93 to 94, its redness decreased, and its yellowness significantly increased. The jujube Yakju that was fermented with 1.5-percent dried jujube had high sensory evaluation (selection rate) scores for color, flavor, taste and overall acceptability. It had no significant changes in pH and total acidity during its storage after its heat treatment. Its soluble solids contents tended to decrease with its heat treatment and to increase in its storage period. With respect to its color changes during its storage, the higher the ratio of the jujube that was added, the longer the storage period was, the lightness (L) and redness (a) decreased and the yellowness (b) increased. The polyphenol contents depended on the rate of addition of the dried jujube, but were not affected by the heat treatment and storage period. The organic acids in jujube Yakju were citric acid, succinic acid, lactic acid, malic acid and acetic acid.

• Solar Energy
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• v.19 no.1
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• pp.19-27
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• 1999

In this study, basic design data which were required for development of highly efficient ice storage system with low temperature latent heat were experimentally obtained. The ice storage system considered in this study was the one that has been widely used in the developed country and called the ice-on-coil type. Using the system, the ice storage performance for various design parameters which were the flow direction and the inlet temperature of the secondary fluid was tested. In addition, the clockwise variation of the heat transfer characteristics of the PCM in the ice storage tank were investigated. During the melting processes in the ice storage tank with several vertical tubes, decrease of the solid-liquid interface area, which was the heat transfer area, between the floating ice and the water made the decreasing rate of IPF less. Also, the total melting energy for the upward flow of the secondary fluid was higher than that for the downward flow during the melting process, but this trend did not appear if the initial temperature of the PCM was $4^{\circ}C$. The average ice recovery efficiency for the upward flow of the secondary fluid was higher than that for the downward flow.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.3
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• pp.234-240
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• 2015

In the face of the world's growing energy storage needs, liquid hydrogen offers a high energy density solution for the storage and transport of energy throughout society. A 5 L liquid hydrogen storage tank has been designed, fabricated and tested to investigate boil-off rate of liquid hydrogen. As the insulation plays a key role on the cryogenic vessels, various insulation methods have been employed. To reduce heat conduction loss, the epoxy resin-based insulation supports G-10 were used. To minimize radiation heat loss, vapor cooled radiation shield, multi-layer insulation, and high vacuum were adopted. Mass flow meter was used to measure boil-off rate of the 5 L cryogenic vessel. A series of performance tests were done for liquid nitrogen and liquid hydrogen to compare with design parameters, resulting in the boil-off rate of 1.7%/day for liquid nitrogen and 16.8%/day for liquid hydrogen at maximum.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.82-88
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• 2013

There are the stirring test and drain test in the daily performance test to determine the thermal performance of a domestic solar hot water system. The drain test is a test that measures the discharge heating rate while drain the hot water from the top of the storage tank and supply the city water to the bottom of the tank. From the perspective of the user, this drain test is more effective than the stirring test. In this study, the thermal performance were compared through the drain test for a passive type and an active type domestic solar hot water systems consisting of the same storage tank and collectors. At this point, a passive type was used the horizontal storage tanks, and an active type was used vertical storage tank. In the drain test, when the hot water drained up to the reference hot water temperature, an active type which have vertical storage tank represents excellent daily performance than a passive type which have horizontal storage tank regardless of weather conditions. The reason for this is because the vertical storage tank is advantageous to thermal stratification in the tank. After the drain test, the residual heat for the horizontal storage tank was much more than the vertical storage tank, but in the next day the amount of discharged heat were less than the those of vertical storage tank neither. Thus, the solar water heating system which have horizontal storage tank should be adopted preheating control method rather than separate using control method when connected with auxiliary heat source device.

• Solar Energy
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• v.7 no.2
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• pp.22-29
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• 1987

This paper dealed with thickness variation of bottom heat sotrage zone due to salinity and flow rate of extration hot brine in small test solar pond (0.5m wide, 0.5m high, 1.0m long). Testing apparatus and situation were follows: 7.1 cm of height of suction diffuser and 1.8cm of height of discharge diffuser above the test pond respectively, 0.3cm of slot size of suction diffuser, 1.0cm of slot size of discharge diffuser, 47cm of length of the slot; heating of hot water ($75^{\circ}C$) through separated hot water tank, discharge of the brine into storage zone through discharge diffuser, the extration of the brine through suction diffuser, circulation of the extracted brine through a heat exchanger (cooler). Following results were obtained through the experiments. 1. In small test solar pond, the typical three zone which showed up in real solar pond were established. 2. Richardson Number was used more effectively to confirm hydrodynamic stability of the stratified flow. 3. The thickness of non convective layer had a great effect on the heat storage of the bottom convective layer, then the temperature of bottom convective layer had a relation to that of upper convective layer. 4. Optimum operating condition in the test pond was on 10%-15% of salt concentration and $0.05m^3/hr$ of flow rate of extraction hot brine. 5. Following thickness of 3 zones were available to obtain under optimum operation condition: o bottom storage zone: $30%{\pm}10%$ of total pond depth o non-convective zone: $40%{\pm}10%$ of total pond depth o Upper surface zone: $20%{\pm}10%$ of total pond depth.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.525-533
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• 2022

In this study, in order to numerically analyze the heat flow characteristics in the valve according to the opening rate for the solenoid valve for hydrogen supply applied to the hydrogen storage tank, flow characteristics were comparatively analyzed. Through the analysis of pressure and temperature distributions within the valve according to the high-pressure supply condition of 70 MPa or more, the heat flow characteristics in the valve, inlet and outlet passage according to the opening rate of the valve were identified. As a result a sudden change in the fluid behavior appears in the neck region of the valve, and it is understood that the flow separation caused by the flow path shape of the expanded tube has a dominant influence on the flow characteristics. And, it was confirmed that the shape of the valve seat is a factor significantly affecting the improvement of flow rate and differential pressure performance.