• Title/Summary/Keyword: 열전달

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A Study of The Effect of Corrosion on Heat Transfer in a Heat Exchanger (열교환기에서 부식이 열전달에 미치는 영향에 관한 연구)

  • Kwon, Hyun-Min;Kwon, Jeong-Tae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.9
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    • pp.227-232
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    • 2019
  • Heat pump systems based on ocean thermal energy conversion (OTEC) systems use the temperature difference between deep ocean water and surface ocean water to operate. However, they may have heat transfer degradation due to corrosion on the heat exchanger surface due to the salinity of sea water. This study presents experimental results for the heat transfer decrease of corroded metal tubes with respect to corrosion time. In order to replace high-priced titanium, electro-deposition (ED) coating was performed on aluminum tubes. Aluminum tubes with ED coating thicknesses of 10, 15, and $20{\mu}m$ were tested for double-tube heat exchangers after performing accelerated corrosion for 6, 12, and 18 weeks. The effects of the coating thickness and the corrosion time on the heat transfer degradation were investigated. From the results, the aluminum tube with an ED coating of $20{\mu}m$ thickness can be suggested as a candidate for replacing titanium tubes.

Effects of Rib Angles on Heat Transfer in a Divergent Square Channel With Ribs on One Wall (한 면에 리브가 설치된 확대 정사각 채널에서 리브 각이 열전달에 미치는 효과)

  • Lee, Myung Sung;Ahn, Soo Whan
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.6
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    • pp.609-613
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    • 2015
  • In this study, the experiments are performed to investigate the local heat transfer and pressure drops of developed turbulent flows in the diverging square channels along the axial distance. The square divergent channels are manufactured with a fixed rib height (e) = 10 mm. Four different parallel angled ribs ($a=30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$) are placed on the channel's one-sided wall only. TThe measurement are conducted within the range of Reynolds numbers from 22,000 to 79,000. The results show that a rib angle-of-attack of $45^{\circ}$ produces the best heat-transfer performance.

Transient Heat Transfer and Structural Analyses for the Turbopump Turbine of a Liquid Rocket Engine (액체 로켓 터보 펌프 터빈의 천이 열전달 및 구조 해석)

  • Yoo, Jae-Han;Choi, Ji-Hoon;Lee, In;Han, Jae-Hung;Jeon, Seong-Min;Kim, Jin-Han
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.3
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    • pp.58-65
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    • 2004
  • Thermal and structural finite element analyses were performed for the turbopump turbine bladed disk model with shroud of a liquid rocket engine. The only 1/80 part model was analyzed which consists of 3D eight node isoparametric solid elements. The applied loading history consists of a startup condition with a thermal spike and a steady state. Heat transfer coefficient on the blade was predicted using the commercial Navier-Stokes solver, Fluent. Transient thermal responses during startup and steady states were calculated using a 3D finite element code developed. Maximum stress and shroud tip displacement under the influence of centrifugal and thermal loading were also determined.

A Study on the heat transfer characteristics of a normal axisymmetric under-expanded impinging jet on a surface (수직 축대칭 과소팽창 충돌 제트의 표면 열전달 특성 연구)

  • Yu, Man-Sun;Kim, Byung-Gi;Cho, Hyung-Hee;Hwang, Ki-Young;Bae, Ju-Chan
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.8
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    • pp.84-91
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    • 2005
  • An experimental investigation has been carried out to examine heat-transfer characteristics of an axisymmetric, under-expanded, sonic jet impinging on a flat plate and the local measurement of surface pressures and heat transfer coefficients on a plate have been achieved together with a visualization test of shock structure in a jet. Heat transfer coefficients on a plate have been found to be changed significantly depending on the under-expansion ratio as much as the nozzle-to-plate distance. These phenomena could be explained by the wall pressure measurement and the shock visualization.

Numerical Heat Transfer Analysis applying Coupled Electromagnetic Characteristics and Convection Boundary Condition (전자계 결합특성 및 대류 경계조건을 적용한 수치 해석적 열전달 해석)

  • Kim, Chang-Ki;Kim, Shang-Hoon;Jung, Sang-Yong
    • Journal of IKEEE
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    • v.13 no.3
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    • pp.55-61
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    • 2009
  • The heat transfer analysis applying finite element method has been carried out. Particularly, the convection boundary condition associated with the mixed boundary condition is numerically formulated by the Galerkin method analogous to the magnetic field problem. Also, the coupled electromagnet-thermal field analysis by the proposed heat transfer coefficient computation algorithm is executed to enhance the accuracy of solutions. Finally, the validity of the proposed results is verified by comparison with the measured ones.

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Heat Flow of Round Jet Impinging Aluminum Foam Mounted on the Heated Plate with Constant Heat Flux (균일한 열유속을 갖는 가열된 평판에 부착된 발포알루미늄에 대한 원형 충돌제트의 열유동 특성)

  • Han, Young-Hee;Lee, Kye-Bock;Lee, Chung-Gu
    • Journal of Energy Engineering
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    • v.18 no.2
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    • pp.108-113
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    • 2009
  • An experimental study of jet impingement on aluminum foam mounted on the surface with constant heat flux is conducted with the presentation of the heat transfer rate measured when jet impinges normally to a flat plate. Effects of pore density, foam thickness and Reynolds number on the heat transfer are analyzed. Experimental results show that the significant enhancement in Nu is obtained when the aluminum foam is mounted on the heated plate and that the increase in the heat transfer due to the porous material insertion is dominated by both the increase in the heat transfer area and the decrease in the momentum flux resulted from the pressure drop.

Pool Boiling Heat Transfer in a Vertical Annulus with a Longer Outside Tube (외부 튜브 길이가 긴 수직 환상공간 내부의 풀비등 열전달)

  • Kang, Myeong-Gie
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.8
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    • pp.775-782
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    • 2012
  • To investigate pool boiling heat transfer in a vertical annulus with closed bottoms, the length of an outer tube was varied between 0.3 and 0.6 m. For the test, a heated tube of 0.2-m length and 19.1-mm diameter and water at atmospheric pressure were used. To elucidate the effects of the outer tube length on heat transfer, the results for the annulus were compared with data for a single unrestricted tube. The increase in the outer tube length resulted in an increase or decrease in heat transfer depending on the gap size. This tendency is mainly attributed to the difference in the intensity of liquid agitation.

Heat Transfer from Rectangular Fins with a Circular Base (원형 베이스와 사각 휜 주위의 열전달 해석)

  • Yu, Seung-Hwan;Lee, Kwan-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.5
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    • pp.467-472
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    • 2011
  • The heat transfer over a radial heat sink, adapted for LED (light emitting diode) downlights, was experimentally and analytically investigated. We added radiation heat transfer into a previous calculation that neglected this factor. The numerical results agreed well with experimental results. Parametric studies were performed to compare the effects of the geometric parameters (fin length, fin height, ideal number of fins) and the operating parameter (heat flux) on the average heat-sink temperature from the heat-sink array. We found the fin length that maximizes the heattransfer performance. As the emissivity increased, the effect of geometric parameters on the radiation heat transfer decreased.

Derivation of Subcompartment Heat Transfer Correlation from HDR Tests (HDR 실험에 근거한 격납용기 구분방내의 열전달 상관식 도출)

  • Lee, Un-Chul
    • Nuclear Engineering and Technology
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    • v.19 no.2
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    • pp.77-84
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    • 1987
  • Statistical evaluation for the heat transfer correlation in the containment subcompartments is carried out from HDR experimental data. Heat transfer data for three HDR blowdown tests, V.42, V.43 and V.44, are analyzed to deduce the correlation. As Uchida already proposed, air-to-steam density ratio is proven to be the most affecting parameter in this study. Here Uchida heat transfer correlation is revised by including temperature difference between the atmosphere and the wall surface, and atmospheric pressure. In addition to these dependencies, atmospheric turbulence and time factor may be included in the model. This implication, however, is not successful, because turbulence and transient phenomena were not adequately quantified in the HDR program. It is concluded that a strong correlation exists between the heat transfer coefficient and temperature differences, specially for forced circulation conditions.

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가장자리를 경사지게 만든 슬랩바닥에 대한 계절별 열손실량의 계산

  • Kusuda T.;Mizumo M.;Bean J. W.
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.11 no.4
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    • pp.34-54
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    • 1982
  • DOE-2, BLAST AND NBSLD와 같은 광범위한 에너지 해석 프로그램에 의거하여 효과적으로 가장자리를 경사지게 만든 슬랩에서의 열전달 계산을 할 수 있도록 그 바닥에서 일어나는 열전달 계산을 재현하였다. 슬랩 바닥면으로부터의 깊이에 따른 매달의 평균 온도를 만들어내기 위해 Lachenbruch 방법에 근거를 둔 수치해석 과정을 깊이 연구하였다. Lachenbruch방법으로 얻어진 자료들을 사용하여 슬랩 바닥면으로부터의 깊이에 따른 매달의 평균 온도를 결정하는 간단한 과정을 만들어냈다. 또한, 이 슬랩에서의 열전달을 매 시간별 레스폰스 인자로 해석하는 데에도 이 매달 평균 온도의 자료들을 사용하였다.

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