• Title/Summary/Keyword: 국소열전달특성

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A Study on the Local Heat Transfer Characteristics for Circular Tubes Using Heat Transfer Promoter (열전달촉진체를 사용한 원관에서의 국소열전달 특성에 관한 연구)

  • Kwon Hwa-Kil;Yoo Seong-Yeon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.5
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    • pp.389-396
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    • 2006
  • For the successful design of heat exchangers, it is very important to understand local heat transfer phenomena on the circular tube of heat exchangers. In the present study, experiments are performed for single circular tube and tube banks with and without heat transfer promoters. The naphthalene sublimation technique is employed to measure the local mass transfer coefficients, and the measured local mass transfer data are converted to the local heat transfer data using heat and mass transfer analogy. The distribution pattern of local Nusselt numbers on single circular tube with heat transfer promoters is similar to that without the heat transfer promoter, but average Nusselt numbers are greatly increased. In case of tube banks without the heat transfer promoter, the Nusselt numbers are much lower in the first row than those of other rows, but the local heat transfer coefficients on all rows are equalized when the heat transfer promoter is installed.

Local Heat Transfer Characteristics on Fin Surface of Plate Fin - Oval Tube with Delta Wing Vortex Generators (Plate fin-oval tube 열교환기에서 와류발생체에 의한 fin 표면에서의 국소 열전달 특성)

  • Shin, Seok-Won;Chung, In-Kee;Kim, Soo-Youn
    • Proceedings of the KSME Conference
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    • pp.2390-2395
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    • 2007
  • The present research was experimentally performed to analyze the effect of delta-wing vortex generators(DWVG) on the heat transfer of fin surface of the plate fin-oval tube. The local heat transfer coefficient of the fin surface for four kinds of DWVG's arrangement was measured by the naphthalene sublimation technique for Reynolds numbers ranging from 2000 to 3200. The results showed that the heat transfer of the plate fin-oval tube can be significantly enhanced by DWVG for relatively low Reynolds numbers.

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Local Heat Transfer Characteristics of Array Impinging Jets with Channel flow on the Concave Surface (채널유동성분이 존재하는 오목 충돌면에서 배열충돌제트에 의한 국소 열전달 특성 고찰)

  • Lee, Won-Hee;Hwang, Sang-Dong;Cho, Hyung-Hee
    • Proceedings of the KSME Conference
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    • pp.1098-1103
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    • 2004
  • In this study, the effect of channel flow in the concave surface on local heat transfer characteristics of array jets was investigated experimentally. A TLC method is employed to determine local heat transfer coefficients on the target plate and also flow visualization has been conducted to investigate the behavior of a row of impinging jets and array of impinging jets. Two different array patterns of impinging array jets devices are tested for Reynolds number(Re=10,000). In a row of impinging jets, secondary vortex is strongly maintained by main vortex at nozzle-to-plate distance of H/d=2. Therefore, the Nusselt number slowly decreased at the mid-way region between adjacent jets. In array jets, the local maximum Nusselt number region move further in the downstream direction due to the increase of channel flow velocity.

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Local Heat Transfer Characteristics in the Wake Region of a Circular Cylinder (원형 실린더 후류 영역의 국소 열전달 특성)

  • Chang Byong Hoon
    • Journal of Energy Engineering
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    • v.14 no.1
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    • pp.30-36
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    • 2005
  • This paper reports the experimental study of the heat transfer characteristics of the wake region behind a cylinder in cross flow. Local heat transfer coefficient was measured from the stagnation point (θ=0°) to 180°, and the variation of Nu in the axial direction along the cylinder was also studied. The results show that the heft transfer rate at the rear (θ=180°) near the duct wall can increase as much as 58% over the 2 dimensional value at the center of the duct. The heat transfer profiles in the wake region also show distinct effects of the aspect ratio and the heat transfer boundary condition.

Local Heat Transfer Characteristics in Convective Partial Boiling by Impingement of Free-Surface/Submerged Circular Water Jets (미세 원형 충돌수제트의 부분 대류비등에 있어서 자유표면/잠입 제트의 국소 열전달 특성)

  • 조형희;우성제;신창환
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.6
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    • pp.441-449
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    • 2002
  • Single-phase convection and partial nucleate boiling in free-surface and submerged jet impingements of subcooled water ejected through a 2-mm-diameter circular pipe nozzle were investigated by local measurements. Effects of jet velocity and nozzle-to-imping-ing surface distance as well as heat flux on distributions of wall temperature and heat transfer coefficients were considered. Incipience of boiling began from far downstream in contrast with the cases of the planar water jets of high Reynolds numbers. Heat flux increase and velocity decrease reduced the temperature difference between stagnation and far downstream regions with the increasing influence of boiling in partial boiling regime. The chance in nozzle-to-impinging surface distance from H/d=1 to 12 had a significant effect on heat transfer around the stagnation point of the submerged jet, but not for the free-surface jet. The submerged jet provided the lower cooling performance than the free-surface jet due to the entrainment of the pool fluid of which temperature increased.

Heat Transfer of Array Impinging Jet on Concave Surfaces with Rectangular Fin (사각 핀이 설치된 오목충돌면에서 배열충돌제트의 국소 열전달 특성 고찰)

  • Oh, Sang-Hyun;Lee, Won-Hee;Lee, Dong-Hyun;Cho, Hyung-Hee;Kim, Mun-Young;Lee, Sung-Ho
    • Proceedings of the SAREK Conference
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    • pp.1149-1154
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    • 2008
  • The present study investigates the heat transfer characteristics on concave surface with array impinging jet and fin arrangement. The heat transfer coefficients was measured by TLC method. The Reynolds number based on jet hole diameter is 10,000 and hole diameter-to-plate distance ratio (H/d) is fixed at 2. The rectangular fins are installed in the curved channel and the width of fin varies from 1d to 3d. Without fins, the averaged heat transfer coefficients decreases as moves downstream region. While, the rectangular fins block the crossflow and higher heat transfer rates were observed compared to smooth channel.

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