• Title/Summary/Keyword: Horizontal aluminum tubes

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Heat Transfer Enhancement Characteristics for Falling-Film Evaporation on Horizontal Enhanced Tubes with Aqueous LiBr Solution (LiBr 수용액을 이용한 수평관 유하액막 증발의 촉진관 전열향상 특성)

  • Kim, Dong Kwan;Kim, Moo Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.9
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    • pp.1267-1276
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    • 1998
  • Falling-film evaporation experiments with aqueous lithium bromide (LiBr) solution were performed to investigate the heat transfer characteristics of enhanced copper tubes. Enhanced tubes (a knurled tube, a spirally grooved tube, and a tube coated with $20{\mu}m$ aluminum particles) and a bare tube were selected as test specimens. Averaged evaporation fluxes of water were obtained from horizontal tubes with various film Reynolds numbers, system pressures, LiBr concentrations and degrees of wall superheat. The enhanced performance of steam generation was compared between tubes with varying parameters. The knurled tube geometry showed the most excellent performance among the tubes tested. The specified enhanced tubes were more useful for generating steam on a low grade heat source such as waste heat.

A STUDY ON EXPERIMENTAL CHARACTERISTICS OF ENERGY ABSORPT10N CONTROL IN THIN-WALLED TUBES FOR THE USE OF VEHICULAR- STRUCTURE MEMBERS

  • Kim, S.-K.;Im, K.-H.;Hwang, C.-S.;Yang, I.-Y.
    • International Journal of Automotive Technology
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    • v.3 no.4
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    • pp.137-145
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    • 2002
  • Automobiles should be designed to meet the requirements and standards for the protections of passengers in a car accident. One of safety factors is an absorbing capacity in collision. Many vehicles have been designed based on the criterion of the absorbing capacity. Therefore a controller has been developed in order to control and increase the absorbing capacity of impact energy in automobile collision. The capacity of impact energy will be improved regardless of vehicular-structure members and shapes. An air-pressure horizontal impact tester for crushing has been built up for the evaluation of energy absorbing characteristics in collision. Influence of height, thickness and clearance in the controller have been considered to predict and control the energy absorbing capacity. Aluminum alloy (Al) tubes (30,39,44 m in inner dia. and 0.8, 1.0, 1.2 m in thickness) are tested by axial loading. The energy absorbing capacity of Al tubes have been estimated in cases of with-controller and without-controller. respectively based on height. thickness, clearance of an controller.

Flow Condensation Heat Transfer Coefficients of R22, R410A and Propane in Aluminum Multi-Channel Tube (알루미늄 다채널 평판관내 R22, R410A, Propane의 흐름 응축 열전달 성능 비교)

  • Park Ki-Jung;Lee Ki-Young;Jung Dongsoo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.7
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    • pp.649-658
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    • 2005
  • Flow condensation heat transfer coefficients (HTCs) of R22, R410, Propane (R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of $0.1\~0.9$ at mass flux of $200\~400kg/m^2s$ and heat flux of $7.3\~7.7kW/m^2$ at the saturation temperature of $40^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within $25\%$ deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than $20\%$ for all data.

Flow Condensation Heat Transfer Coefficients of R22 Alternative refrigerants in Aluminum Multi-Channel Tube (알루미늄 다채널 평판관내 R22 대체냉매의 흐름 응축 열전달 성능 비교)

  • Lee, Ki-Young;Lee, Min-Hang;Jung, Dong-Soo
    • Proceedings of the SAREK Conference
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    • 2005.11a
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    • pp.249-255
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    • 2005
  • Flow condensation heat transfer coefficients(HTCs) of R22, R4IO, Propane(R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53 m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of 0.1 ${\sim}$ 0.9 at mass flux of $200{\sim}400$ $kg/m^2s$ and heat flux of $7.3{\sim}7.7$ $kW/m^2$ at the saturation temperature of $4^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within 25% deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than 20% for all data.

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A Comparison of Flow Condensation HTCs of R22 Alternatives in the Multi-Channel Tube (다채널 알루미늄 평판관내 R22와 R134a의 흐름 응축 열전달 성능 비교)

  • 서영호;박기정;정동수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.6
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    • pp.589-598
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    • 2004
  • Flow condensation heat transfer coefficients (HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4 mm hydraulic diameter and 0.53 m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1∼0.9 at mass flux of 200∼400 kg/$m^2$s and heat flux of 7.3∼7.7 ㎾/$m^2$ at the saturation temperature of 4$0^{\circ}C$. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heat-ing or cooling type heat transfer experimental apparatus.

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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    • 2004.11a
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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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The effects of non-condensable gas on condensation heat transfer on a super-hydrophobic surface tube (초소수성 코팅 튜브에서의 비응축가스 영향에 대한 응축 열전달 연구)

  • Ji, Dae-Yun;Kim, Daeho;Lee, Kwon-Yeong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.4
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    • pp.517-524
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    • 2018
  • This purpose of this research is to observe the influence of non-condensable gas (NCG) on a horizontal super-hydrophobic aluminum tube and compare it with a bare aluminum tube. To achieve super-hydrophobic characteristics, an aluminum tube was coated with a Self-Assembled Monolayer (SAM). The overall heat transfer coefficient U was used to represent the condensation performance. The NCG mass fraction was the main variable, and its range was 0.08 to 0.45. The condensation performance of the SAM tube and bare tube increased with decreasing mass fraction of NCG. The SAM tube showed 1.9 to 2.5 times larger dropwise condensation performance than the bare tube. When the mass fraction of NCG decreased in the SAM tube, the rate of increase of the SAM tube was lower because flooded condensation occurred. In addition, filmwise condensation occurred in the SAM tube when more active condensation was generated, and its performance was lower than that of the bare aluminum tube. The flooded and filmwise condensation in the SAM tube is explained by the pinning effect. In conclusion, controlling the condition of the condenser is necessary to improve the condensation performance by surface modification a SAM.