• Title/Summary/Keyword: Rapid Cooling System

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High Performance Gear Obtained by Die Warm Compaction and Rapid Cooling Process

  • Calero, J.A.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.199-200
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    • 2006
  • PM recent developments focus on increasing this technology's competitiveness when compared to wrought materials. Warm compaction allows the replacement of a double press double sinter process with a single warm press and sintering step, thus allowing cost and time savings. Moreover there are added benefits to consider such as reducing work in process and lessening part's logistics cost. This paper presents a successful industrial trial to replace a double press-double sinter process with a warm die compaction and sintering process. The part chosen was a high performance gear containing 0,9% wt. carbon. Sintering was conducted in a belt furnace at $1120^{\circ}C$ in a nitrogen rich atmosphere with rapid cooling process in order to obtain a quasi fully martensitic structure with a minimum of 700HV0,1 and 450HV10 after annealing. The balance between properties and cost is favoured by the use of a singular lubricant developed in a Eureka frame project together with POMETON S.A. and die warm compaction. Warm compaction is only needed to be effective on the gear teeth, in order to achieve the required properties. Therefore only the die is actually heated. This simplified system avoids flow rate problems typically involved when using more elaborate warm compaction equipments.

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Study of the Performance of the Fin-Tube Heat Exchanger of the Miniature Joule-Thomson Refrigerator (쥴톰슨냉동기의 열교환기 성능에 관한 연구)

  • Hong, Yong-Ju;Kim, Hyo-Bong;Park, Seong-Je;Choi, Young-Don
    • Progress in Superconductivity and Cryogenics
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    • v.11 no.1
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    • pp.55-59
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    • 2009
  • Miniature Joule-Thomson refrigerators have been widely used for rapid cooling of infrared detectors, probes of cryosurgery, thermal cameras, missile homing head and guidance system, due to their special features of simple configuration, compact structure and rapid cool-down characteristics. The thermodynamic performance of J-T refrigerator highly depends on the hydraulic and heat transfer characteristics of the recuperative heat exchanger. The typical recuperative heat exchanger of the J-T refrigerator has the double helical tube and fin configuration. In this study, effectiveness-NTU approach was adopted to predict the thermodynamic behaviors of the heat exchanger for the J-T refrigerator. The thermodynamic properties from the REFPROP were used to account the real gas effects of the gas. The results show the effect of the operating conditions on the performance of the heat exchanger and refrigerator for the given heat exchanger. The influences of mass flow rate and the supply pressure on the effectiveness of heat exchanger and the ideal cooling capacity are discussed in details.

Experimental Analysis of Process Variables in Rapid Prototyping Technique by Using Projection Welding (프로젝션 용접을 이용한 쾌속조형법에서 공정변수의 실험적 해석)

  • Lee Sang-Chan;Park Jeong-Nam
    • Journal of Welding and Joining
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    • v.23 no.2
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    • pp.47-51
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    • 2005
  • Rapid Prototyping (RP) technology has helped successfully to reduce time and costs since first emerged in 1986. Recently, RP using functional materials like as metal have been researched. However RP using molten metal and brazing material have been struggling to resolve several drawbacks, such as dimensional inaccuracy, poor surface finish and post finishing because occurring shrinkage and warpage at cooling. So, the purpose of this study is to develop a new RP technique using sheet metal and projection welding for reducing several drawbacks in occurring RP using molten metal. And optimum process variables were determined using desist of experiment(DOE).

Resistivity Variation of Nickel Oxide by Substrate Heating in RF Sputter for Microbolometer

  • Lee, Yong Soo
    • Journal of Sensor Science and Technology
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    • v.24 no.5
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    • pp.348-352
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    • 2015
  • Thin nickel oxide films formed on uncooled and cooled $SiO_2/Si$ substrates using a radio frequency (RF) magnetron sputter powered by 200 W in a mixed atmosphere of argon and oxygen. Grazing-incidence X-ray diffraction and field emission scanning electron microscopy are used for the structural analysis of nickel oxide films. The electrical conductivity required for better bolometric performance is estimated by means of a four-point probe system. Columnar and (200) preferred orientations are discovered in both films regardless of substrate cooling. Electric resistivity, however, is greatly influenced by the substrate cooling. Oxygen partial pressure increase during the nickel oxide deposition leads to a rapid decrease in resistivity, and the resistivity is higher in the cooled nickel oxide samples. Even when small microstructure variations are applied, lower resistivity in favor of low noise performance is acquired in the uncooled samples.

Experiments on the Heat Transfer and Pressure Drop Characteristics of a Channel with Pin-Fin Array (핀-휜을 삽입한 채널의 열전달 및 압력강하 특성 실험)

  • 신지영;손영석;김상민;이대영
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.7
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    • pp.623-629
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    • 2004
  • Rapid development of electronic technology requires small size, high density packaging and high power of electronic devices, which result in more heat generation by the electronic system. Present cooling technology may not be adequate for the thermal management in the current state-of-the-art electronic equipment. Forced convective heat transfer in a channel filled with pin-fin array is studied experimentally in this paper as an alternative cool-ing scheme for a high heat-dissipating equipment. Various configurations of the pin-fin array are selected in order to find out the effect of spacing and diameter of the pin-fin on the heat transfer and pressure drop characteristics. In the low porosity region, interfacial heat transfer and pressure drop seem to show different trend compared to the conventional heat transfer process.

The Study on the Corrosion Characteristics of Al-Alloy Shell for Cooler (알루미늄합금 원통냉각기의 부식 특성에 관한 연구)

  • 임우조;김성진;윤병두
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.39 no.2
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    • pp.152-157
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    • 2003
  • Most Recently, with rapid development in marine industries such as marine structures and ship, there occurs much interest in the study of corrosion characteristics which play an important role in design of cooling water system like heat-exchanger. Especially, as operating environment of fresh cooling water system in vessels is acidified, this system is seriously corroded. In this study, to study on the corrosion characteristics of Al-alloy shell for cooler, the electrochemical polarization test of materials for the marine fresh water cooler such as Al-alloy, Cu and naval brass was carried out in fresh water. And thus the polarization resistance and anodic polarization behavior of Al-alloy, Cu and naval brass are investigated. Also, galvanic corrosion characteristics of Al-alloy coupled with Cu and naval brass is considered. The main results obtained are as follows ; (1) The current density of corrosion is high in order of Al-alloy > naval brass > Cu (2) As anodic potential increases, the corrosion resistance of naval brass is better than that of Cu. (3) The galvanic corrosion of Al-alloy coupled with Cu and naval brass is activated than corrosion of Al-alloy.

A Performance Evaluation of a Heat Dissipation Design for a Lithium-Ion Energy Storage System Using Infrared Thermal Imaging (적외선 열화상을 활용한 리튬 이온 ESS의 방열설계 성능평가에 관한 연구)

  • Kim, Eun-Ji;Lee, Gyung-Il;Kim, Jae-Yeol
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.5
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    • pp.105-110
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    • 2020
  • The global battery market is rapidly growing due to the development of vehicles(EV) and wireless electronic products. In particular logistics robots, which hielp to produce EVs, have attracted much interest in research in Korea Because logistics sites and factories operate continuously for 24 hours, the technology that can dramatically increase the operation time of the logistics equipment is rapidly developing, and various high-level technologies are required for the batteries used in. for example, logistics robots. These required technologies include those that enable rapid battery charging as well wireless charging to charge batteries while moving. The development of these technologies, however, result in increasing explosions and topical accidents involving rapid charging batteries These accidents due to the thermal shock caused by the heat generated during the charging of the battery cell. In this study, a performance evaluation of a heat dissipation design using infrared thermal imaging was performed on an energy storage systrm(Ess) applied with an internal heat conduction cooling method using a heating plate.

Effects of the initial charging pressure of gas on the cool-down characteristics of the Joule-Thomson cryocooler (초기충전압력이 쥴톰슨냉동기의 강온에 미치는 영향)

  • Hong, Yong-Ju;Park, Seong-Je;Choi, Young-Don
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2160-2164
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    • 2008
  • Miniature Joule-Thomson cryocoolers have been widely used for rapid cooling of infrared detectors, probes of cryosurgery, thermal cameras, missile homing head and guidance system, due to their special features of simple configuration, compact structure and rapid cool-down characteristics. The cool-down time, the temperature at the cold end, the running time and the gas consumption are the important indicators of the performance of the J-T cryocooler. In this study, the initial cool-down stages of the J-T cryocooler were investigated by numerical simulations. The results show the effects of the initial charging pressures of gas on the cool-down time and the temperature at the cold end and the gas consumptions.

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A study on coil temperature bariation in 75% hydrogen batch annealing furnace (75% 수소 BATCH 소둔시에서의 코일 온도변화에 관한 연구)

  • Jeon, Eon-Chan;Kim, Soon-Kyung
    • Journal of the Korean Society for Precision Engineering
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    • v.11 no.2
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    • pp.173-181
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    • 1994
  • A Cold spot temperature control system for the batch annealing furnace has been estabilished in order to reduce energy consumption to improve productivity and stabilize the propertics of products. Therefore we confirmed a relation between annealing cycle time and atmospheric gas, variation of coil cold spot temperature with time during heating and actual temperature measurements at mid-width of each coil during heating and actual temperature measurements at mid-width of each coil during soaking. The results of the tempaeature variation effect on the batch annealing are as follows. 1) Heating time is reduced to one half with increasing atmospheric gas flow rate and changing of atmospheric gas component from HNx to Ax gas, and annealing cycle time is reduced to 2.7 times. 2) In case of short time healing, the slowest heating part is the center of B coil, in case of long time heating, the low temperature point moves from the center of coil to inside coil. And the temperature in this part is higher than other parts when cooling. When finished heating, the cold spot is located 1/3 of coil inside in case of HNx atmospheric gas. But center of coil in case of Ax atmospheric gas. 3) The outside of top coil is the highest temperature point when heating, which becomes the lowest temperature point when cooling. So, this point becomes high temperature zone at heating and low temperature zone at cooling, It has relation according to atmospheric gas component and flow rate. 4) Soaking time at batch annealing cycle determination is made a decision by the input coil width, and soaking time for quality homogenization of 1214mm width coil must be 2.5 hours longer than that of 914mm width coil for the same ciol weight. 5) Annealing cycle time with Ax atmospheric gas is extended 1 hour in of slow cooling during 5 hours in order to avoid rapid cooling.

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A Performance Evaluation of Concrete for Low-carbon Eco-friendly PC Box for Near-surface Transit System (저심도 철도시스템 구축을 위한 저탄소 친환경 PC 박스용 콘크리트의 성능 평가)

  • Koh, Tae-Hoon;Ha, Min-Kook;Jung, Ho-Jin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.5
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    • pp.3587-3595
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    • 2015
  • Low-carbon eco-friendly precast concrete (PC) box structure has been recently was developed as an low-cost infrastructure of near-surface transit system. The concrete of PC box was manufactured by industrial byproducts such as ground granulated blast furnace (GGBF) slag, flyash and rapid-cooling electric arc furnace (EAF) oxidizing slag, its mechanical property and durability were estimated in this study. Based on the mechanical and durability tests, it is found that low-carbon eco-friendly concrete shows high initial compressive strength, more than 90% of design strength (35MPa), and high resistance to salt-attack, chemical- attack and freeze-thaw. Therefore, low-carbon eco-friendly PC box concrete technology is expected to contribute to the railway with low environmental impact.