• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.45-50
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• 2013

Closed-loop J-T (Joule-Thomson) refrigeration cycle is advantageous compared to common open loop $N_2$ decompression system in terms of nitrogen consumption. In this study, two closed-loop pure $N_2$ J-T refrigeration systems with sub-atmospheric device for cooling High Temperature Superconductor (HTS) power cable are investigated. J-T cooling systems include 2-stage compressor, 2-stage precooling cycle, J-T valve and a cold compressor or an auxiliary vacuum pump at the room temperature. The cold compressor and the vacuum pump are installed after the J-T valve to create sub-atmospheric condition. The temperature of 67 K is possible by lowering the pressure up to 24 kPa at the cold part. The optimized hydrocarbon mixed refrigerant (MR) J-T system is applied for precooling stage. The cold head of precooling MR J-T have the temperature from 120 K to 150 K. The various characteristics of cold compressor are invstigated and applied to design parameter of the cold compressor. The Carnot efficiency of cold compressor system is calculated as 16.7% and that of vacuum pump system as 16.4%. The efficiency difference between the cold compressor system and the vacuum pump system is due to difference of enthalpy change at cryogenic temperature, enthalpy change at room temperature and different work load at the pre-cooling cycle. The efficiency of neon-nitrogen MR J-T system is also presented for comparison with the sub-atmospheric devices. These systems have several pros and cons in comparison to typical MR J-T systems such as vacuum line maintainability, system's COP and etc. In this paper, the detailed design of the subcooled $N_2$ J-T systems are examined and some practical issues of the sub-atmospheric devices are discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.1032-1037
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• 2011

In this study, simulation and optimization works for a demethanizer column have been performed to obtain ethane and heavier products from a pretreated natural gas stream. Pretreated natural gas feed stream was partially condensed after being precooled by exchanging heat with demethanizer top vapor stream and by using an external refrigeration cycle with a propane refrigerant. Vapor stream was cooled further and partially condensed through a turbo-expander. The power generated from the expansion of turbo-expander was delivered to the compressor for the residue gas compression. Liquid stream was cooled by Joule-Thomson expansion valve and was fed to the middle section of the demethanizer. Recovery percent of ethane for feed natural was set to 80% and methane to ethane molar ratio was fixed as 0.0119. On the other hand, some of the cold heat could be recovered by splitting the feed stream and by exchanging heat with side reboiler in order to reduce the heat duty in the propane refrigeration cycle.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.1
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• pp.11-19
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• 1994

An optimal design for Gifford-McMahon/Joule-Thomson(GM-JT) refrigerators was performed by a numerical method. The design goal was to meet the cooling requirement for MRI systems, which was 3 Watt at 4 K. A general cycle analysis program was written to calculate the cooling capacity of the GM-JT refrigerators for the givenstage GM refrigerator. The program was executed for a specific refrigerator with various design parameters. The optimal values for the maximum cooling were found for the sizes of the heat exchangers, the mass flow rate of helium, and the compression pressure.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.181-185
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• 2008

The new concept for liquefaction of natural gas has been designed and simulated in this paper. Conventional liquefaction cycles are usually composed with Joule-Thomson valves at lower temperature refrigerant cycle. The new concept of natural gas liquefaction is discussed. The main difference with conventional liquefaction process is the presence of the turbine at low temperature of MR (mixed refrigerant) cycle. The turbine acts as expander but also as an energy generator. This generated energy is provided to the compressor which consumes energy to pressurize refrigerants. The composition of the mixed refrigerant is investigated in this study. Components of the refrigerant are methane, propane and nitrogen. Composition for new process is traced with Aspen HYSYS software. LNG heat exchangers are analyzed for the new process. Heating and cooling curves in heat exchangers were also analyzed.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.60-63
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• 2009

Most J-T (Joule-Thomson) refrigerators use a Giaque-Hampson type heat exchanger due to its excellent thermal performance and compactness. The cryoprobe (cryosurgical probe) treating prostate cancer usually has a dimension of 17 gauge (1.6 mm diameter), so it does not have enough space to bear a Giaque-Hampson type heat exchanger. In this paper, the triplet heat exchanger is adopted as the heat exchanger of cryoprobe, and the performance is investigated with an experimental test. The result shows that the triplet heat exchanger can be substituted for Giaque-Hampson type heat exchanger in the application of cryosurgery.

• Design & Manufacturing
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• v.17 no.3
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• pp.61-66
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• 2023

In this study, we developed a simulation methodology for a technology that rapidly cools molds by directly spraying them with CO₂ in its liquefied gaseous state. Initially, a simulation verification process was conducted using ANSYS Fluent's heat transfer analysis based on temperature values measured in prior research experiments, ensuring a comparable temperature could be calculated. Subsequently, the validated analysis method was employed to evaluate design factors that exert the most significant influence on cooling. An evaluation was conducted based on three factors: part thickness, mold thickness, and the melting temperature of material. Using a full factorial design approach, a total of 27 analyses were completed and subsequently calculated through analysis of means. The impact assessment was carried out based on the temperature values at the product's core. The results indicated that the thickness of the mold had the highest influence, while the melting temperature of material had the least.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.1013-1019
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• 2011

In this paper, simulation works for a multi-stage cascade refrigeration cycle using propane, ethylene and methane as refrigerants have been performed for the liquefaction of natural gas using Peng-Robinson equation of state built-in PRO/II with PROVISION release 8.3. The natural gas feed compositions were supplied from Korea Gas Corporation and the flow rate was assumed to be 5.0 million tons per annual. Supply temperature for propane refrigerant was fixed as $-40^{\circ}C$, that for ethylene refrigerant as $-95^{\circ}C$, and that for methane refrigerant as $-155^{\circ}C$. For the multi-stage refrigeration cycle, three-stage refrigeration was assumed for propane refrigeration cycle, two-stage refrigeration for ethylene refrigeration cycle and three-stage refrigeration for methane refrigeration cycle. Natural gas was finally cooled and liquefied to $-162^{\circ}C$ by Joule-Thomson expansion. Conclusively, 91.71% by mole of the natural gas liquefaction ratio was obtained through a cascade refrigeration cycle and Joule-Thomson expansion and 0.433 kW of compression power was consumed for the liquefaction of 1.0 kg/hr of natural gas.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.5
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• pp.609-616
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• 2018

The cargo handling system, which is composed of a fuel gas supply unit and cargo tank pressure control unit, is the second largest power consumer in a Liquefied Natural Gas (LNG) carrier. Because of recent enhancements in ship efficiency, the surplus boil-off gas that remains after supplying fuel gas for ship propulsion must be reliquefied or burned to regulate the cargo tank pressure. A full or partial liquefaction process can be applied to return the surplus gas to the cargo tank. The purpose of this study is to review the current partial liquefaction process for LNG carriers and develop new processes for reducing power consumption using exergy analysis. The developed partial liquefaction process was also compared with the full liquefaction process applicable to a LNG carrier with a varying boil-off gas composition and varying liquefaction amounts. An exergy analysis showed that the Joule-Thomson valve is the key component needed for improvements to the system, and that the proposed system showed an 8% enhancement relative to the current prevailing system. A comparison of the study results with a partial/full liquefaction process showed that power consumption is strongly affected by the returned liquefied amount.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.1
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• pp.10-17
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• 2003

The steady and transient thermal and flow analysis for liquid helium using for the pressurization of liquid rocket propellant tanks have been conducted numerically. The required inner diameter of helium channel that satisfy the design mass flow rate and velocity, through the steady state analyses for various thermal conditions at the wall, is determined and it is found that due to the sign of Joule-Thomson coefficient of helium, the temperature of helium increase monotonically for adiabatic wall condition. The temporal behavior of helium temperature, density, velocity are also investigated under the existence of local heat inflow on the wall.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.81-88
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• 2009

Bellows is used to control temperature of a Joule-Thomson micro cryocooler. It is made of Nickelcobalt alloy that retains mechanical properties from cryogenic temperature to temperature of 570K. The geometry of bellows is an axisymmetric shell and Nitrogen with high pressure was charged at temperature of 293K. During cool-down process, the pressure and volume of Nitrogen are changed and must be satisfied with state equation. At cryogenic temperature, Nitrogen can exist as a part liquid and part vapor. Pressure-density-temperature behavior under this vaporliquid phase equilibrium is closely given by the Modified-Benedict-Webb-Rubin(MBWR) state equation. To evaluate deformation of bellows for temperature change, the numerical calculation of the volume within bellows and finite element analysis of bellows under internal pressure were iteratively performed until MBWR state equation is satisfied. The numerical results show that deformation of the bellows can be analyzed by the present method in a wide range of temperature including cryogenic temperature.