• 제목/요약/키워드: Thermal storage material

검색결과 268건 처리시간 0.031초

초기적으로 과냉각된 수직실린더 내부 물질의 상변화 과정 (Phase change process of the initially subcooled material in a vertical cylinder)

  • 백영렬;이재헌
    • 대한기계학회논문집B
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    • 제21권1호
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    • pp.24-35
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    • 1997
  • Melting process inside in a vertical cylinder has been investigated numerically to observe heat transfer characteristics in the latent heat storage vessel applied to the thermal storage system. The time-dependent boundary fitted coordinate system was introduced to overcome the difficulty caused by the moving boundary. The present results are in good agreement with the available previous data when the initial subcooling effect of the solid phase is not considered. It is found that the melting is promoted by the natural convection, but is delayed by the initial subcooling effect of the solid phase.

형상기억합금을 이용한 HDD Load/Unload 서스펜션의 설계 (Design of HDD Load/Unload Suspension Using Shape Memory Alloy)

  • 임수철;박영필;박노철;최승복
    • 정보저장시스템학회논문집
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    • 제2권1호
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    • pp.71-78
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    • 2006
  • In this work, we propose a new type of HDD Load/Unload(L/UL) suspension featuring shape memory alloy(SMA). The mechanical and thermal properties of the SMA film with respect to the material phase states are experimentally estimated and the SMA film is carefully integrated to the suspension. In order to obtain the desirable dynamic characteristics of the suspension during L/UL process, the design parameters of the SMA film such as geometric properties are determined by considering the vibration modes of the suspension related to the L/UL performance. After analyzing the modal characteristics of the proposed suspension, L/UL performance is evaluated through L/UL simulation by observing the vibration motion and minimum flying height of the slider during L/UL process.

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다양한 직경의 속이 빈 탄소구체의 제조 및 리튬 저장 특성 (Synthesis of Hollow Carbon Spheres with Various Diameters and Their Lithium Storage Properties)

  • 신슬기;조혁래;정용재;구상모;오종민;신원호
    • 한국전기전자재료학회논문지
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    • 제36권1호
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    • pp.10-15
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    • 2023
  • The carbonaceous materials have attracted much attention for utilization of anode materials for lithium-ion batteries. Among them, hollow carbon spheres have great advantages (high specific capacity and good rate capability) to replace currently used graphite anode materials, due to their unique features such as high surface areas, high electrical conductivities, and outstanding chemical and thermal stability. Herein, we have synthesized various sizes of hollow carbon spheres by a facile hardtemplate method and investigated the anode properties for lithium-ion batteries. The obtained hollow carbon spheres have uniform diameters of 350 ~ 600 nm by varying the template condition, and they do not have any cracks after the optimization of the process. Increasing the diameter of hollow carbon spheres decreases their specific capacities, since the larger hollow carbon spheres have more useless spaces inside that could have a disadvantage for lithium storage. The hollow carbon spheres have outstanding rate and cyclic performance, which is originated from the high surface area and high electrical properties of the hollow carbon spheres. Therefore, hollow carbon spheres with smaller diameters are expected to have higher specific capacities, and the noble channel structures through various doping approaches can give the great possibility of high lithium storage properties.

자연대류 영향을 고려한 상변화 열에너지 저장장치의 열전도향상에 관한 수치적 연구 (Numerical Study on Enhanced Heat Conduction of Phase-Change Thermal Energy Storage Devices in The Presence of Natural Convection)

  • Chung, Hong-Chul
    • 한국안전학회지
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    • 제8권4호
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    • pp.207-212
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    • 1993
  • 상변화 에너지 저장장치는 변동하는 액체-고체 상접합면과 자연대류의 존재에 기인한 비선형성 때문에 해석적으로 분석하기가 어렵다. 핀(fin) 형태의 상변화 에너지 저장장치를 준선형화 시켜 열전달을 수치적으로 해석하여 실험 데이타와 비교 검증하였다. 대칭형 수평 핀에 대하여 준선형, 비정상의 얇은 2차원적 모델을 세우고 유한체적방법(FVM)에 의해 시간의 함수로 융해된 상변화물질의 비율과 액체-고체 상접합면의 형상을 예측하였다. 유한체적방법(FVM)에 의한 결과는 실험결과와 비교적 잘 일치하였다. 벽과 융해점 사이의 온도차가 클수록 융해된 상변화물질의 비율은 증가하였으며 대류항을 포함하는 경우가 없는 경우보다 실험결과에 더 가까운 해를 얻을 수 있었다.

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ZnO 나노선 - Au 나노입자 하이브리드 메모리 소자 (A ZnO nanowire - Au nanoparticle hybrid memory device)

  • 김상식;염동혁;강정민;윤창준;박병준;김기현;정동영;김미현;고의관
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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    • pp.20-20
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    • 2007
  • Nanowire-based field-effect transistors (FETs) decorated with nanoparticles have been greatly paid attention as nonvolatile memory devices of next generation due to their excellent transportation ability of charge carriers in the channel and outstanding capability of charge trapping in the floating gate. In this work, top-gate single ZnO nanowire-based FETs with and without Au nanoparticles were fabricated and their memory effects were characterized. Using thermal evaporation and rapid thermal annealing processes, Au nanoparticles were formed on an $Al_2O_3$ layer which was semi cylindrically coated on a single ZnO nanowire. The family of $I_{DS}-V_{GS}$ curves for the double sweep of the gate voltage at $V_{DS}$ = 1 V was obtained. The device decorated with nanoparticles shows giant hysterisis loops with ${\Delta}V_{th}$ = 2 V, indicating a significant charge storage effect. Note that the hysterisis loops are clockwise which result from the tunneling of the charge carriers from the nanowire into the nanoparticles. On the other hand, the device without nanoparticles shows a negligible countclockwise hysterisis loop which reveals that the influence of oxide trap charges or mobile ions is negligible. Therefore, the charge storage effect mainly comes from the nanoparticles decorated on the nanowire, which obviously demonstrates that the top-gate single ZnO nanowire-based FETs decorated with Au nanoparticles are the good candidate for the application in the nonvolatile memory devices of next generation.

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미립잠열슬러리의 물성에 관한 실험적 연구 (Physical Properties of Microencapsulated Phase Change Material Slurries)

  • 이효진;홍재창;이재구
    • 설비공학논문집
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    • 제12권9호
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    • pp.860-869
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    • 2000
  • The thermal conductivity and density of slurries entrained with the particles of Micro-PCM are measured with respect to its temperatures as well as concentrations. For the thermal conductivity of slurries, a device made from P.A. Hilton (Model No. H470) is adopted. There is a well-scaled 0.3 mm gap between shells into which the slurry is injected. The temperatures of the slurry are changed to $5~25^{\circ}C$ , for which it is controled by the supplied voltage and cooling water circulated around the outer shell. The concentrations of Micro-PCM slurries are varied from 5 wt% to 50 wt%. Some general equations such as Maxwell's equation, are evaluated for their applicability with Micro-PCM slurry. As a result, it happens to be some 20% discrepancy between the experiment and the applied equations. The density measurements of Micro-PCM slurry to its temperature and concentration are peformed by hydrometer. For the experiment, tetradecane encapsulated slurry (($t_m≒6^{\circ}C$) and a mixed wax ($t_m≒50^{\circ}C$) are tested. The temperature changes of tetradecane are applied for $0^{\circ}C\;to\;$20^{\circ}C$and a mixed wax for $20^{\circ}C\;to\;$60^{\circ}C$ and its concentrations are changed from 5 wt% to 30 wt%. The results are compared with a general equation and the referenced data. For the conclusion, the experimental result and a general equation are well agreed.

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차등 3$\omega$ 기법을 이용한 다층 유전체 박막의 열전도도 측정 및 검증 (Measurement and Verification of Thermal Conductivity of Multilayer Thin Dielectric Film via Differential 3$\omega$ Method)

  • 신상우;조한나;조형희
    • 정보저장시스템학회:학술대회논문집
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    • 정보저장시스템학회 2005년도 추계학술대회 논문집
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    • pp.254-259
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    • 2005
  • In this study, measurement of thermal conductivity of multilayer thin dielectric film has been conducted via differential 3$\omega$ method. Also, verification of differential 3$\omega$ method has been accomplished with various proposed criteria. The target film for measurement is 300 nm silicon dioxide and this thin film is covered with various thicknesses of upper protective layer. The upper protective layer is inserted between the target film and the heater line for purpose of electrical insulator or anti-oxidation barrier since the target film may be a good electrical conductor or a well-oxidizing material. However, the verification of differential 3$\omega$ method has not been conducted. Thus we have shown that the measurement of thermal conductivity of thin films with upper protective layer via differential 3$\omega$ method is verified to be reliable as long as the proposed preconditions are satisfied. Experimental results show that the experimental errors tend to increase with aspect ratio between upper protective layer thickness and width of the heater line due to heat spreading effect.

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다양한 파우더 충전 단열 방법의 단열 성능에 대한 실험적 연구 (Experimental research about thermal insulation performance of various powder insulation methods)

  • 김희선;정상권;정성하
    • 한국초전도ㆍ저온공학회논문지
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    • 제12권3호
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    • pp.49-54
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    • 2010
  • This paper presents apparent thermal conductivity of various powder at different vacuum levels for cryogenic insulation. Four kinds of powder insulator are examined by using boil-off calorimetry at pressure range from 50 Torr to 3 mTorr. The first material is perlite which is widely used in cryogenic application. Microsphere is the second one that is recently proposed as a replacement powder for liquid hydrogen storage tanks. It is a hollow sphere made of silica with the diameter in the order of 10 to $100{\mu}m$. Popped rice and polystyrene beads are also selected as candidates for powder insulation even though they are polymers. With their porous elliptic and spherical configuration and light density, they demonstrate fairly good thermal insulation performance at pressure range from 50 Torr to 3 mTorr. According to the experimental investigation in this paper, microsphere and polystyrene beads possess promising insulation characteristic as powder insulators and further study is desired.

철도차량 차체용 탄소섬유/에폭시 복합재의 환경노화 특성 평가 (Environmental aging characteristics of carbon/epoxy composite for train carbody)

  • 오진오;윤성호;김정석;한성호
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2007년도 추계학술대회 논문집
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    • pp.824-829
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    • 2007
  • Mechanical and thermal analysis properties of carbon fiber/epoxy composite for train carbody were evaluated by varying with environmental factors such as ultraviolet, temperature, and moisture. Accelerated environmental aging tester was utilized for this study. Testing temperature was set to $80^{\circ}C$ and ultraviolet was obtained through xenon-arc lamp. To consider moisture, water sprayed on specimen for 18 minutes every 2 hour. All the specimens were made of CF1263/Epoxy composite. Mechanical properties such as tensile, bending, and shear properties were evaluated through a material testing system. Also, thermal analysis properties such as storage shear modulus, loss shear modulus, and tan ${\delta}$ were measured through dynamic mechanical analyzer. Finally surfaces of the composite exposed to environmental factors were examined using a scanning electron microscope. From experimental results, those properties of CF1263/Epoxy composite were shown to be slightly decreased due to environmental factors.

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상변화 물질로부터의 열에너지 추출에 관한 연구 - 핀이 부착된 열싸이폰 이용에 관하여 - (Thermal Energy Extraction from Phase Change Material - by Means of Finned Thermosyphon -)

  • 목재균;유재석;김기현
    • 태양에너지
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    • 제8권1호
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    • pp.5-12
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    • 1988
  • One of the effective means to transfer the heat into and from the energy storage medium is thermosyphon. In this study, a two-phase closed thermosyphon with circular fins was used to extract the thermal energy stored in paraffin wax (Sunoco p-116). Heat transfer characteristics along the heat flow path were investigated as well as the overall performance. Some of the important results are as follows: (1) The temperature distribution of the wax in the radial direction was always maintained fairly uniformly; (2) Compared with bare thermosyphon, the heat transfer rate was vastly improved in the early stage of the experiment; and (3) Heat transfer coefficient between the wax and evaporating section of thermosyphon remained nearly constant during the experiment.

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