• Journal of Energy Engineering
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• v.8 no.4
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• pp.576-582
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• 1999

this paper presents the results of experiments on subsooling degree characteristics which was analyzed in accordance with various test conditions. The test water was cooled below freezing point temperature, was measured. The results showed that using city water as the test water in pyrex tube indicated small standard deviation (SD) compared to using distilled water, and minimum subcooling degree was 6.9$^{\circ}C$ and 6.2$^{\circ}C$, respectively. In addition, a critical subcooling degree in a pyrex tube was larger than that in a stainless steel tube about 0.7$^{\circ}C$ for the same test water. It was also observed that the standard deviation of data for the distilled water showed decreasing tendency aw the increasing with cooling velocity. Then metaldehyde showed a considerable effect on the subcooling degree of distilled water as the ice nucleating substance with increase of test number.

• Journal of Energy Engineering
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• v.9 no.3
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• pp.178-183
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• 2000

본 연구에서는 유동과 냉각수를 이용하는 아이슬러리 제조관정을 관찰하고, 이 시스템의 가장 큰 문제점인 관내동결 특성을 파악하였다. 시험수로는 수도수(city water)를 이용하였다. 시스템을 순환하는 시험수가 제빙관내에서 $0^{\circ}C$ 이하의 과냉각 조건이 형성되어 제빙관을 빠져 나오면서 축냉조에 설치된 충격판상에서 과냉각 해소가 일어났다. 이때 유동과냉각수는 내부에너지를 방출하면서 그 일부가 얼음 입자로 상변화되었고, 나머지는 실험장치를 계속순환하였다. 제빙관에서 시험수와 브라인의 열교환 방식을 대향류와 평행류 두 조건에서 시험수의 과냉각도는 Reynolds 수가 증가함에 따라 감소하는 경향을 보였고, 이들 결과 값으로부터 각각의 관계식을 유도하였다. 또한 브라인의 냉각속도가 0.29~0.53[$^{\circ}C$/min] 범위에서 시험수의 과냉각도는 브라인 냉각속도에 종속되지 않았다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1080-1083
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• 2017

In the design of KSLV-II, there is a scenario in which supercooled liquid oxygen is supplied to prevent a geysering phenomenon in the oxidizer pipe and a cavitation phenomenon at the pump inlet. To verify this condition in the engine development test phase, a system that supplies supercooled liquid oxygen to the engine was applied in the engine combustion test facility. In this system, supercooling methods using a vacuum ejector and using helium injection to the tank were appied. Both tests were carried out for about 17 minutes. Supercooling results of about 3.3K for the ejector test and about 2.2K for the helium injection test were obtained at the 50% level of the tank.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.5
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• pp.580-585
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• 2012

In this paper, the cycle performance analysis for condensation and evaporation capacity, total work and efficiency of ocean thermal energy conversion power system using R744 ($CO_2$) is presented to offer the basic design data for the operating parameters of this system. The operating parameters considered in this study include superheating and subcooling degree, evaporation and condensation temperature, pump and turbine efficiency. The main results were summarized as follows : The evaporation capacity of R744 increases with superheating and subcooling degree, but decreases with the increasing condensation temperature. The total work increases with superheating and subcooling degree of R744, but decreases with the increasing evaporating temperature. And, the efficiency increases with subcooling and superheating degree, but decreases with the increasing condensation temperature. Therefore, superheating and subcooling degree, evaporation and condensation temperature and pump and turbine efficiency of R744 OTEC power system have an effect on the evaporation and condensation capacity, total work and efficiency of this system. With a thorough grasp of these effect, it is necessary to design the OTEC power cycle using R744.

• 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.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.134-142
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• 2006

Sub-cooling of cryogenic propellant by helium injection is one of the most effective methods for suppressing bulk boiling and keeping sub-cooled liquid oxygen before rocket launch. In order to design the cooling system, understanding of the limitations of heat and mass transfer is required. In this paper, an analytical model for the helium injection system is presented. This model's main feature is the representation of bubbling system using finite-rate heat transfer and instantaneous mass transfer concept. With this simplified approach, the effect of helium injection to liquid oxygen system under several circumstances is examined. Experimental results along with simulations of single bubble rising in liquid oxygen and bubbling system are presented with various helium injection flow rates, and with change of oxygen chamber pressure.

• Solar Energy
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• v.10 no.2
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• pp.28-37
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• 1990

A study was conducted to investigate the feasibility of using a super-absorbent polymer made from a acrylic acid copolymer for a capsule-type ice storage system. In a simple pyrex-tube test, 25% of distilled water samples tested turned out not be frozen at all at $-12^{\circ}C$ and the average supercooling of the samples frozen was $9.8^{\circ}C$. With the addition of 0.5wt% super-absorbent polymer, however, the supercooling of the distilled water was dramatically reduced and more than 35% of samples tested did not show any supercooling. The heat transfer characteristics of a capsule-type ice storage unit was also investigated with a distilled water as the phase-change material. With the addition of 0.5wt% polymer, the supercooling of water was not observed at all and thus an overall heat transfer was enhanced. Based on these results, it was concluded that a super-absorbent polymer is a potential candidate as the nucleating agent for an ice-storage system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.578-584
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• 2013

Ice slurry that is a mixture of fine ice crystals and liquid water is a widely used working fluid in the ice thermal energy storage system due to its flowability and large latent heat of fusion. Generally ice slurry is made from supercooled water. But the excessive supercooling causes the water to freeze even worse to block the pipe. Additionally large degree of supercooling of water degrades the efficiency of the ice thermal energy storage system. Therefore the effective method to control the phase change from supercooled water to ice slurry is needed. In this paper we experimentally studied a novel method to generate the ice slurry from the supercooled water using the ultrasonic vibration. It was found that the cavitation impact of supercooled water by ultrasonic vibration can help the generation of ice slurry.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.437-444
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• 2012

This paper describes the experimental characteristics on cooling and heating performance of the coil deposition type heat pump using geothermal energy to optimize the design for the operating parameters of this system. The operating parameters considered in this study include subcooling degree, evaporation and condensation temperature in the coil deposition type heat pump using geothermal energy. The main results are summarized as follows : As the evaporation temperature and subcooling degree of the coil deposition type heat pump using geothermal energy increases, and the condensation temperature decreases, the COP of this system increases. The subcooling degree, evaporation and condensation temperature of the coil deposition type heat pump have an effect on cooling and heating COP of this heat pump. Therefore, it is a necessary to determine the optimum operation conditions for the highest COP of this heat pump presented in this study.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.29 no.7
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• pp.60-67
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• 2000

현재까지 많은 공조용 빙축열 시스템이 전력수요 평준화를 목적으로 개발되어 설비에 적용되어 왔다. 지금까지 각종 학회에서 발표된 내용들은 기업에서 개발된 빙축열 시스템의 제빙 방식의 특징이나 시운전 결과가 중심이고, 빙축열 시스템의 평가, 특히 실제 설비의 운전 데이터에 기초한 시스템 성능 평가에 대한 내용은 많지 않았다. 이번에 소개하고자 하는 기술은 현장 제조형의 과냉각 방식 빙축열시스템의 실제 설비를 대상으로 제빙조의 제빙성능과 해빙성능에 관하여 모델해석를 기초로 평가하고, 제빙효율, 소비전력, 운전비용과 관련하여 설명함으로서 열원시스템을 평가하고자 한다.