• Progress in Superconductivity and Cryogenics
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• v.12 no.4
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• pp.41-45
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• 2010

Miniature Joule-Thomson refrigerators have been widely used for rapid cooling of infrared detectors, optoelectronic device, and integrated circuits of micro electronics. The typical J-T refrigerator consists of the recuperative heat exchanger with the double helical tube and fin configuration, J-T nozzle, a mandrel, Dewar and a compressed gas storage bottle. In this study, to predict the thermodynamic behaviors of the refrigerator with a compressed gas storage bottle during the cool-down time, numerical study of transient characteristics for a J-T refrigerator was developed. A simplified transient one.dimensional model of the momentum and energy equations was simultaneously solved to consider the thermal interactions of the each component of the refrigerator. To account for effects of the thermal mass of the solid, the heat capacities of the tube, fins, mandrel and Dewar are considered. The results show the charged gas pressure of the gas storage bottle has significant effects on the performance of the J-T refrigerator. At the elevated gas pressure of the gas storage bottle, the large capacity of the compressed gas storage does not need to get the fast cool-down performance of the J-T refrigerator in the cool-down stage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.528-536
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• 2002

As one step for the safety performance of LNG storage tank, the change in fracture toughness within the X-grooved weld heat-affected zone (HAZ) of newly developed 9% Ni steel, which was submerged arc (SA)-welded, was investigated. Both crack initiation fracture toughness and crack arrest fracture toughness were evaluated by the crack tip opening displacement (CTOD) tests and compact crack arrest (CCA) tests. As the evaluated region approached the fusion line, each test result shorted different tendency, that is, crack initiation toughness decreased while crack arrest toughness increased. The results were discussed through the observation of the microstructural change.

• Journal of Conservation Science
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• v.38 no.1
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• pp.72-79
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• 2022

A paulownia wood has been widely used with various advantages as its low weight, permeability, convenient workability and aesthetic patterns for a long time. However, the related empirical researches and simultaneous evaluations of functionality are insufficient compared with acid-free archival boxes for now. In this study, the indoor and outdoor temperature and relative humidity control and heat release rate were evaluated under the controlled and uncontrolled circumstance in 2018. The paulownia wood storage box showed superior control effect of relative humidity than the acid-free archival box in constantly uncontrolled environment. Also, the possibility of the flame diffusion from the surface of the materials was higher for the paulownia materials, and the acid-free archival box showed more dangerous patterns in the early stages of the fire.

• Polymer(Korea)
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• v.39 no.1
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• pp.23-32
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• 2015

Phase change materials based on ultra high molecular weight of polyethylene (UHMWPE) blended with paraffin wax (mp $65^{\circ}C$) were studied in this paper. In addition, this paper reviews recent studies on the preparation of shape stabilized phase change materials (SSPCM), such as SSPCM from UHMWPE and paraffin wax (mp $65^{\circ}C$), their basic properties and possible applications to latent heat storage. The preparation method was an absorption method. Also, SSPCM composites were prepared by using a hot press at $200^{\circ}C$ for 10 min. The analysis for the shape ability of SSPCM to improve heat efficiency was measured by FTIR, SEM, DSC, XRD, and ARES. UHMWPE composites with 30 wt% paraffin wax (mp $65^{\circ}C$) demonstrated less deterioration of physical property and effective thermal property compared with other conditions. As a result, these SSPCMs could be used for the heat storage and release materials for various products.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.13 no.1
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• pp.28-35
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• 1984

• Journal of Hydrogen and New Energy
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• v.26 no.5
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• pp.431-437
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• 2015

Recently, a miniaturized measurement cell of effective thermal conductivity was developed to evaulate the heat transfer characteristics of hydrogen stroage material in the initial step of its development. In this work, the realiablity issues which can occur from this miniaturization of measurement cell were studied in detail by both experiments and numerical simulation of heat transfer. $LaNi_5$ as a reference was used for the reliability evaluation of the miniaturized measurement cell. Numerical simulations of heat transfer for this measurement system were verified through comparison with the experimental data. Under these reliablity studies, we discuss how to overcome the inherent drawbacks of this miniaturized system in order to achieve the high reliability.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.5-6
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• 2011

CO₂ reduction is the most urgent issue the world is facing. So, there should be a measure to reduce the CO₂ emission in construction industry which has more released CO₂ gas than other industries. CO₂ emission of building depend on using energy. Then efficient energy use process working efficiently at CO₂ reduction. Therefore In this study, author find the technical possibility of saving the building energy using the PCM which is able to control heat, storage heat and potential heat. So, it considered that apply to floor heating type which is major heating system of living space in Korea. And evaluate the Using possibility.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.8
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• pp.426-431
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• 2015

The advantages of a printed circuit heat exchanger (PCHE) are the compactness and efficiency derived from its heat-transfer characteristics; furthermore, a PCHE for which a diffusion bonding method was used during production can be applied to extreme environments such as a cryogenic condition. In this study, a micro-channel PCHE fabricated by diffusion bonding was investigated in a cryogenic environment regarding its thermal performance and the pressure drop. The test rig consists of an LN2 storage tank, vaporizers, heaters, and a cold box, whereby the vaporized cryogenic nitrogen flows in hot and cold streams. The overall heat-transfer coefficients were evaluated and compared with traditional correlations. Lastly, we suggested the modified heat-transfer correlations for a PCHE in a cryogenic condition.

• Journal of Hydrogen and New Energy
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• v.32 no.5
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• pp.324-330
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• 2021

In recent years, polymer electrolyte membrane fuel cell (PEMFC) based cogeneration system has received more and more attention from energy researchers because beside electricity, the system also meets the residential thermal demand. However, the low-quality heat exited from PEMFC should be increased temperature before direct use or storage. This study proposes a method to utilize the heat exhausted from a 10 kW PEMFC by coupling a heat pump. Two different configuration using heat pump and a reference layout with heater are analyzed in term of thermal and total efficiency. The system coefficient of performance (COP) increases from 0.87 in layout with heaters to 1.26 and 1.29 in configuration with heat pump and cascade heat pump, respectively. Lastly, based on system performance result, another study in economics point of view is proposed.

• Journal of Biosystems Engineering
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• v.16 no.4
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• pp.399-407
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• 1991

In Korea, the cultivation area under the plastic greenhouse was 1,746 ha in 1975, and 36,656 ha in 1989, it shows that the greenhouse cultivation area was increased by 21 times during last 14 years. The greenhouse cultivation area of 90~93% has been kept warm with double layers of plastic film and thermal curtain knitted with rice straw, and the rest area of 7~10% has been heated by fossil fuel energy. The use of rice straw thermal curtain is inconvenient to put it on and off, on the other hand the use of fossil fuel heating system results in the increase of production cost. To solve these problems, at first the heating load and the storable solar energy in greenhouse during the winter season were predicted to design solar utilization system, secondly a solar thermal storage system filled with latent heat storage materials was developed in this study. And then finally the thermal performance of greenhouse-solar energy storage system was analyzed theoretically and experimentally.