• Journal of the Semiconductor & Display Technology
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• v.23 no.2
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• pp.6-11
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• 2024

This paper presents the design and experimental analysis of a cryogenic refrigeration system for -100 ℃, primarily intended for semiconductor etching process. The refrigeration system utilizes non-flammable mixed refrigerant Joule-Thomson refrigeration cycle, incorporating a precooling stage to enhance overall performance. The selected refrigerants for the system include R1234yf for the precooling stage, and Ar, R14, R23 and R218 for the main cooling stage of the Joule-Thomson refrigeration cycle. Design results according to the system constraints and experimental results are discussed, including lowest evaporation temperature, compressor isentropic efficiency and overall pressure tendencies. The achieved refrigerant fraction from optimal design is Ar: R14: R23: R218 = 0.15: 0.4: 0.15: 0.3, indicating COP of 0.1118 at the isentropic compressor efficiency of 50%. The experimental result shows the developed system reaches steady state in approximately 3 hours.

• Nuclear Engineering and Technology
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• v.28 no.4
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• pp.415-422
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• 1996

Tritium removal from tritiated heavy water in a PHWR is the most effective way in reducing workers' internal dose and radioactivity emissions from Wolsong NPP. The optimum design of the Wolsong TRF (Tritium Removal Facility) was carried out using an approximate short-cut method with an assumption that the TRF, designed to extract 8 MCi per year of elemental tritium from a heavy oater feedstream, uses Liquid Phase Catalytic Exchange (LPCE) front-end process and Cryogenic Distillation (CD) process.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.12
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• pp.32-40
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• 2009

• Clean Technology
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• v.20 no.3
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• pp.314-320
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• 2014

The purpose of this work is to optimize composition of mixture refrigerants used in the C3MR (Propane & Mixed Refrigerants) process by a statistical optimization technique. C3MR studied in this work is one of widely used commercial natural gas liquefaction processes with high efficiency. Process simulation was performed in a commercial process simulator and methane ($C_1$), ethane ($C_2$), propane ($C_3$), and nitrogen ($N_2$) were selected as mixed refrigerants. Using the process model, optimum composition of refrigerants mixture was determined via mixture design and central composite design to produce minimum energy consumption. As a result, it was confirmed that energy consumption is reduced down to 11.3% comparing to existing design. It was also compared with heat effectiveness through temperature profile of MCHE (main cryogenic heat exchanger).

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.125-134
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• 2022

The Global Expansion Roadmap published by the International Space Exploration Coordination Group, which is organized by space agencies around the world, presents future lunar exploration guidance and stresses a lunar habitat program to utilize lunar resources. The Moon attracts attention as an outpost for deep space exploration. Simulating lunar surface environments is required to evaluate the performances of various equipment for future lunar surface missions. In this paper, an experimental study was conducted to simulate high vacuum pressure and cryogenic temperature of the permanent shadow regions in the lunar south pole, which is a promising candidate for landing and outpost construction. The establishment of an efficient dirty thermal vacuum chamber (DTVC) operation process has never been presented. One-dimensional ground cooling tests were conducted with various vacuum pressures with the Korean Lunar Simulant type-1 (KLS-1) in DTVC. The most advantageous vacuum pressure was found to be 30-80 mbar, considering the cooling efficiency and equipment stability. However, peripheral cooling is also required to simulate a cryogenic for not sublimating ice in a high vacuum pressure. In this study, an efficient peripheral cooling operation process was proposed by applying the frost ratio concept.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.2
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• pp.87-92
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• 2015

The injection molding process is widely used in the production of most plastic products. In order to make metal-colored plastic products like those found in modern luxury home alliances, metallic pigments are mixed with a basic resin material for injection molding. However, process control for metal-colored plastic products is extremely difficult due to the non-uniform melt flow of the metallic resin pigments. In this study, the effect of process parameters on the quality of a metal-colored plastic product is evaluated. A rapid mold cooling method using a compressed cryogenic fluid is also proposed to decrease the content of undesired compounds within the plastic product.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.756-761
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• 2012

Natural gas is converted in to LNG by chilling and liquefying the gas to the temperature of $-162^{\circ}C$, when liquefied, the volume of natural gas is reduced to 1/600 of its standard volume. This gives LNG the advantage in transportation. In this study, the effects of the pressure drop of refrigerant and natural gas in the LNG heat exchanger of cryogenic cascade refrigeration cycle were investigated and then the design criteria for the pressure drop of refrigerant and natural gas of the LNG heat exchanger were proposed. The pressure drop of the cascade liquefaction cycle was investigated and simulated using HYSYS software. The simulation results showed that the pressure drop in the LNG heat exchanger is set to 50 kPa considering the increase in the compressor work and COP of cryogenic cascade liquefaction cycle.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.6
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• pp.643-649
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• 2011

For the development of butterfly valves used in liquefied natural gas (LNG) vessels, the seat tightness is one of the important factors to be taken into account in the valve-design process. An O-ring-type metal seal with a retaining ring showing good seat tightness at cryogenic temperatures has been widely used, despite the high manufacturing costs involved. As an alternative, a flexible solid metal seal offers not only sufficient tightness of the butterfly valve, meeting specification requirements, but also relatively low manufacturing costs. In this study, a design criterion to ensure the seat tightness of the butterfly valve using the flexible solid metal seal is proposed. The contact pressure can be calculated by the simulation of the frictional contact behavior between the surface of the metal seal and the valve disc. The geometry of the flexible solid metal seal is determined so that it satisfies the design criterion for sufficient seat tightness, and is verified by experiments according to BS6755 and BS6364.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.3
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• pp.222-229
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• 2012

The cooling of a injector effects on the vapor pressure of cryogenic oxidizer spray, and it decides the phase transition point at the ignition process, when the combustion chamber pressure increases drastically. The phase transition of oxidizer spray affects the ignition characteristics, and several ignition tests with the LOx/$GCH_4$ uni-element coaxial swirl injector was performed in the different initial temperatures of oxidizer injector, in order to investigate the effect of injector cooling on the ignition transient characteristics. At the transition point of oxidizer phase, where the combustion chamber pressure increased over the LOx vapor pressure, the temporary quenching phenomenon of the flame occurred. The lower temperature of chilled down injector and tubing tends to move up the phase transition earlier.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.8-15
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• 2004

This paper presents von Mises stress, deformation, and rotating distortion moment characteristics of inner tank bottom plate as a function of a cryogenic temperature difference along the radial distance from the center area to the corner one. The calculated results show that the filling level of LNG at the beginning of the cool-down process is very important for the design safety analysis of the inner tank. Obviously the thermal loading by a temperature difference between the LNG vapor gas of $-80^{\circ}C$ and a LNG temperature of $-162^{\circ}C$ affects to the thermal related characteristics of the bottom plates and annular one. From the computed results, the temperature difference by a vapor gas and liquid of LNG may lead to the thermal instability of the bottom plate. This phenomenon may cause the system failure of an inner tank.