• Title, Summary, Keyword: Aluminum Tube

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An Experimental study on R-22 Evaporation in Flat Aluminum Multi-Channel Tubes (알루미늄 다채널 평판관내 R-22 증발에 관한 실험적 연구)

  • Kim, Jung-Oh;Cho, Jin-Pyo;Kim, Jong-Won;Jeong, Ho-Jong;Kim, Nae-Hyun
    • Proceedings of the KSME Conference
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    • pp.96-103
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    • 2000
  • In this study, evaporation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the following range of variables ; vapor quality $(0.1{\sim}0.9)$, mass flux$(100{\sim}600kg/m^2s)$ and heat flux$(5{\sim}15kW/m^2)$. The micro-tin tube showed higher heat transfer coefficients compared with those of the smooth tube. Results showed that, for the smooth tube, the effects of mass flux, quality and heat flux were not prominent, and existing correlations overpredicted the data. For the micro-fin tube at low quality, the heat transfer coefficient increased as heat flux increased. However, the trend was reversed at high quality Kandlikar's correlation predicted the low mass flux data, and Shah's correlation predicted the high mass flux data. The heat transfer coefficient of the micro fin tube was approximately two times larger than that of the plain tube. New correlation was developed based on present data.

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Microstructure and Mechanical Properties of CNT/Al Composite Fabricated by a Powder-in-Sheath Rolling Method utilizing Copper Tube as a Sheath (구리튜브를 피복재로 이용한 분말시스압연법에 의해 제조된 CNT/Al 복합재료의 미세조직 및 기계적 특성)

  • Lee, Seong-Hee
    • Journal of Korean Powder Metallurgy Institute
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    • v.21 no.5
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    • pp.343-348
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    • 2014
  • A powder-in-sheath rolling (PSR) process utilizing a copper alloy tube was applied to a fabrication of a multi-walled carbon nanotube (CNT) reinforced aluminum matrix composite. A copper tube with an outer diameter of 30 mm and a wall thickness of 2 mm was used as a sheath material. A mixture of pure aluminum powders and CNTs with the volume contents of 1, 3, 5 vol% was filled in the tube by tap filling and then processed to 93.3% height reduction by a rolling mill. The relative density of the CNT/Al composite fabricated by the PSR decreased slightly with increasing of CNTs content, but showed high value more than 98%. The average hardness of the 5%CNT/Al composite increased more than 3 times, compared to that of unreinforced pure Al powder compaction. The hardness of the CNT/Al composites was some higher than that of the composites fabricated by PSR using SUS304 tube. Therefore, it is concluded that the type of tube affects largely on the mechanical properties of the CNT/Al composites in the PSR process.

Characteristics of thermal stress for thermoelectric generator with sliding (온도차를 이용한 열전발전기의 sliding에 따른 열응력 특성)

  • Woo, B.C.;Lee, H.W.;Lee, D.Y.;Kim, B.S.;Kim, B.G.;Suh, C.M.
    • Proceedings of the KIEE Conference
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    • pp.1904-1906
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    • 1999
  • The purpose of this study is to manufacture and test a thermoelectric generator which converts unused energy from close-at-hand sources, such as garbage incineration heat and industrial exhaust, to electricity. A manufacturing process and the properties of a thermoelectric generator are discussed before simulating the thermal stress and thermal properties of a thermoelectric module located between an aluminum tube and alumina plate. It was shown that the electric voltage of a thermoelectric generator with 128 thermoelectric modules was 4.8 voltage per Kelvin, and the longitudinal stresses of an aluminum tube with a two-point constrained tube could be released more than those with a one-point constrained tube.

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A Study on Bonded Joints of Composite Hollow Bushing (Composite Hollow Bushing의 접합기술에 관한 연구)

  • Cho, Han-Goo;Kang, Hyung-Kyung;Yoo, Dea-Hoon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.493-494
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    • 2008
  • During the last years hollow core insulators started their success story in the field of high voltage engineering for electrical apparatus, substituting porcelain insulators. The termination, also named top and bottom fittings are used for the connection to the rest of the electrical apparatus. The top and bottom flange are attached to the composite to transmit mechanical load and also ensure the gas tightness. They are bonded by epoxy glue with a glass transition temperature of about $130^{\circ}C$-$150^{\circ}C$ the glass reinforced epoxy tube of filament winding. This paper describes the results of a study on the bonded joints of fiber reinforced epoxy tube and cast aluminum. This suggests that surface roughness and glue types play an important role in evaluating of gas sealing capability on the flange and fiber reinforced epoxy tube in the composite hollow bushing.

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An Experimental Study on Laminar Heat Transfer in Flat Aluminum Extruded Tubes Having Small Hydraulic Diameter

  • Kim, Nae-Hyun;Ham, Jung-Ho;Kim, Do-Young
    • International Journal of Air-Conditioning and Refrigeration
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    • v.15 no.2
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    • pp.47-53
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    • 2007
  • Laminar heat transfer experiments were conducted in flat extruded aluminum tubes. Three different flat tubes-two with smooth inner channel, one with micro-finned inner channel-were tested. Smooth tube data were in reasonable agreement with the predictions by simplified theoretical models. The heat transfer coefficients of the micro-fin tube were significantly smaller than those of the smooth tube. The reason was attributed to the decelerating flow in the inter-fin region. Heat transfer correlations were developed from the data.

Development of Ultrafine-Grained Aluminum Tubes Using Severe Plastic Deformation Process (강소성 가공 공정을 이용한 튜브 형상 재료의 결정립 미세화에 대한 연구)

  • Kim, Kyung-Jin;Yoon, Jeong-Whan;Yang, Dong-Yol
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.10
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    • pp.1087-1090
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    • 2009
  • A unique process was developed to improve the mechanical properties of a circular tube. In this proposed process, a large amount of strain is applied to the wall of tube, leading to grain refinement in the material. In order to investigate characteristics of microstructural evolution such as the distribution of grain size and misorientation angle during the process, an EBSD OIM analysis was carried out. The analysis confirms that the proposed process can very effectively produce a circular tube with ultrafine-grains.

High strain rate test of aluminum alloy with torsional Hopkinson bar (비틂홉킨슨봉을 이용한 알루미늄합금의 고속 전단변형 실험)

  • 전병선;유요한;정동택
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.80-83
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    • 1997
  • The split Hopkinson bar technique is the most widely used method to study material behavior at high strain rate deformation. In the present paper, a torsional Hopkinson bar for testing thin-walled tube specimens at high strain rate is described. From the experiment of aluminum 6061, dynamic stress-strain relationship can be obtained and dynamic result is compared with static one.

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Fabrication of Vacuum Tube arrays with a sub-micron dimension using Anodic Aluminum Oxide Nano-Templates

  • Hwang, Sun-Kyu;Lee, Kun-Hong
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.867-869
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    • 2003
  • Vacuum tube arrays (VTA) with a submicron dimension were fabricated by using anodic aluminum oxide (AAO) nano-templates. The field emission characteristics of Ni nanowires show a turn-on voltage in the range of 11.0-14.0 V and a field enhancement factor in the range of 560-2790. The distance between the tips of Ni nanowires and the anode was much smaller than that between the tips and the anode of conventional designs.

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R-22 and R-410A Condensation in Flat Aluminum Multi-Channel Tubes (알루미늄 다채널 평판관내 R-22 및 R-410A 응축에 관한 연구)

  • Jung, Ho-Jong;Kim, Nae-Hyun;Yoon, Baek;Kim, Man-Hoi
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.7
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    • pp.575-583
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    • 2002
  • In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-410A, and the results are compared with those of R-22. Two internal geometries were tested; one with a smooth inner surface and the other with micro-fins. Data are presented for the following range of variables; vapor quality (0.1~0.9), mass flux (200~600 kg/$m^2$s) and heat flux (5~15 ㎾/$m^2$). Results show that the effect of surface tension drainage on the fin surface is more pronounced for R-22 than R-410A. The smaller Weber number for R-22 may be responsible. For the smooth tube, the heat transfer coefficient of R-410A is slightly larger than that of R-22. For the micro-fin tube, however, the reverse is true. Possible reasoning is provided considering the physical properties of the refrigerants. For the smooth tube, a correlation of Akers et at. type predicts the data reasonably well. For the micro-fin tube, the Yang and Webb model was modified to correlate the present data.

A Comparison of Flow Condensation HTCs of R22 Alternatives in the Multi-Channel Tube (알루미늄 다채널 평판관내 R22의 흐름응축 열전달 성능 비교)

  • Seo, Young-Ho;Lim, Dae-Taeg;Park, Ki-Jung;Jung, Dong-Soo
    • Proceedings of the KSME Conference
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    • pp.1270-1275
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    • 2004
  • Flow condensation heat transfer coefficients(HTCs) of R22 and R134a were measured on horizontal aluminum multi-channel tube. The experimental apparatus was composed of three main parts ; a refrigerant loop, a water loop and a water-ethylene glycol loop. The test section in the refrigerant loop was made of aluminum multi-channel tube of 1.4 mm hydraulic diameter and 0.53 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. The data scan vapor qualities $(0.1{\sim}0.9)$, mass flux ($200{\sim}400$ $kg/m^{2}s$) and heat flux ($7.3{\sim}7.7$ $kW/m^{2}$) at $40{\times}0.2^{\circ}C$ saturation temperature in small hydraulic diameter tube. It was found that some well-known previous correlations were not suitable for multichannel tube. So, It must develop new correlations for multi-channel tubes.

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