• Title/Summary/Keyword: Flat Tube

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Thermal and Flow Analysis of the Flat Tube with Micro-Channels (미세유로를 갖는 납작관의 열·유동 해석)

  • Chung, Kilyoan;Lee, Kwan-Soo;Kim, Woo-Seung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.8
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    • pp.978-986
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    • 1999
  • In this study, the general thermal and flow characteristics of flat tube with micro-channels has been studied and the correlation of Nusselt number and friction factor is proposed. The optimal flat tube geometry is determined by optimal design process. It is assumed to be a three dimensional laminar flow in the analysis of thermal and flow characteristics. The periodic boundary condition is applied since the geometry of flat tube with micro-channels shows uniform cross-section in primary flow direction. Local Nusselt number is examined for thermal characteristics of each membrane, and module average Nusselt number and friction factor are calculated to determine the characteristics of the heat transfer and pressure drop in overall flat tube with microchannels. The correlations between Nusselt number and friction factor are given by Reynolds number, aspect ratio of membranes, and the width of flat tube. ALM (Augmented Lagrangian Multiplier) method is applied to the correlations to determine an optimal shape of flat tube. It is shown that the optimal aspect ratio of flat tube is approximately 1.0, irrespective of the width of flat tube and Reynolds number.

Local and Overall Heat Transfer Characteristics of Fin- Flat Tube Heat Exchanger with Vortex Generators

  • Yoo, Seong-Yeon;Chung, Min-Ho;Park, Dong-Seong
    • International Journal of Air-Conditioning and Refrigeration
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    • v.11 no.3
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    • pp.150-157
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    • 2003
  • Local and overall heat transfer characteristics of fin-flat tube heat exchangers with and without vortex generators were investigated. Local heat transfer coefficients were measured with the heat exchanger model using naphthalene sublimation technique. In case of a fin-flat tube heat exchanger without vortex generators, only the horseshoe vortices formed around tubes augment the heat transfer. On the other hand, longitudinal vortices created artificially by vortex generators additionally enhance heat transfer in case of a fin-flat tube heat exchanger with vortex generators. Overall heat transfer coefficients were measured with the prototypes of the fin-flat tube heat exchanger with and without vortex generators in a wind tunnel and results were compared with those of a fin-circular tube heat exchanger with wavy fin. Friction losses for heat exchangers were also measured and compared. The fin-flat tube heat exchanger with vortex generators is found to be more effective than the fin-circular tube heat exchanger with wavy fin.

An Experimental Study on the Local and Overall Heat Transfer Characteristics of a Fin-Flat Tube Heat Exchanger (납작관형 핀-관 열교환기의 국소 및 총합 열전달 특성에 관한 실험적 연구)

  • 유성연;정민호;박동성;이상섭
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.11
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    • pp.939-947
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    • 2002
  • Local and overall heat transfer characteristics of fin-flat tube heat exchangers with and without vortex generators are investigated. Local heat transfer coefficients are measured with the heat exchanger model using naphthalene sublimation technique. In case of a fin-flat tube heat exchanger without vortex generators, only the horseshoe vortices formed around tubes augment the heat transfer. On the other hand, longitudinal vortices created artificially by vortex generators enhance heat transfer dramatically in case of a fin-flat tube heat exchanger with vortex generators. Overall heat transfer coefficients are measured with the prototype of the fin-flat tube heat exchanger with and without vortex generators in a wind tunnel and results are compared with those of a fin-circular tube heat exchanger with wavy fin. Friction losses for heat exchangers are also measured and compared. The fin-flat tube heat exchanger with vortex generators is found to be more effective than the fin-circular tube heat exchanger with wavy fin.

Heat Transfer Performance of Evaporator Used in a Domestic Refrigerator/Freezer Under Frosting Condition (착상을 고려한 가정용 냉동/냉장고 증발기의 열전달 성능)

  • Lee Jang-Seok;Lee Kwan-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.1
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    • pp.62-70
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    • 2005
  • In this study, the air-side heat transfer coefficients of several types of evaporators in the household freezer/refrigerators are investigated. The types considered in this work are: discrete flat plate fin-and-tube type(in-lined tube array), continuous flat plate fin-and-tube type(staggered tube array), and spine fin-and-tube type(in-lined tube array). The heat transfer correlations obtained from this study for each heat exchangers could expect heat transfer coefficients less than $5\%$ of errors. The result indicates that the air-side heat transfer performance of spine fin-and-tube type evaporator shows the highest value under dry conditions, but discrete flat plate fin-and-tube type evaporator shows the highest value among these three evaporators under frosting conditions.

Flow and Thermal Analyses for the Optimal Specification of Flat Tube at Radiator (라디에이터용 납작관의 최적형상 도출을 위한 열.유동해석)

  • Park, Kyoung-Woo;Pak, Hi-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.8
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    • pp.1046-1055
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    • 2000
  • The flow and thermal phenomena in flat tubes of radiator are analyzed numerically. To predict the characteristics of heat transfer and pressure drop, the flow analysis program for three-dimensional complex geometry is developed, which adopted an non-staggered grid system and Cartesian velocities as dependent variables of the momentum equations. Using the developed program, the effect of tube specifications on the heat transfer characteristics is investigated for various flat tubes. From this study, the following results are obtained; (1) For the same hydraulic diameter($D_h{\doteq}5.2$mm), the Nusselt numbers of three basic modeis(D, J, and H-model) are 8.71, 8.92, and 10.58, respectively, and the pressure drops of D-, J-, and H-model are predicted as $-3.08{\times}10^{-2}\;Pa,\;-3.12{\times}10^{-2}\;Pa,\;and\; -3.98{\times}10^{-2}$ Pa, (2) In case of the same flat tube specification, the fins must be brazed at upper tube surface because the heat is more vividly transferred. Therefore, it is found that the H- model is the most effective tube as a heat exchanger and these results are used as a fundamental data for the design of tube.

Heat Transfer Characteristics of Flat Plate Finned-Tube Heat Exchangers with a Variation of Fin Pitch and Number of Tube Row (핀-튜브 열교환기의 핀피치 및 열수 변화에 따른 열전달 성능특성에 관한 연구)

  • Kim Yong-Han;Lee Ho-Seong;Kim Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.10
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    • pp.930-937
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    • 2005
  • The objective of this study is to investigate the heat transfer performance of flat plate finned-tube heat exchangers with large fin pitch. In this study, twenty-two heat exchangers were tested with a variation of fin pitch, number of tube row, and tube alignment. The heat transfer coefficient decreased with a reduction of the fin pitch and an increase of the number of tube row. The staggered tube alignment improved heat transfer performance more than $10\%$ compared to the inline tube alignment. A heat transfer correlation was developed from the measured data for flat plate finned-tubes with large fin pitch. The correlation yielded good predictions of the measured data with mean deviations of $3.6\%\;and\;6.4\%$ for the inline and staggered tube alignment, respectively.

Experimental and Computational Studies of the Pulse Wave Impinging upon a Vertical Flat Plate (수직평판에 충돌하는 펄스파에 관한 실험적/수치해석적 연구)

  • 이동훈;김희동;강성황
    • Journal of KSNVE
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    • v.11 no.2
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    • pp.285-291
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    • 2001
  • The impingement of a weak shock wane discharged from the open end of a shock tube upon a flat plate was investigated using shock tube experiments and numerical simulations. Harten-Yee Total Variation Diminishing method was used to solve axisymmetric, unsteady, compressible flow governing equations. Experiments were carried out to validate the present computations. The effects of the flat plate and baffle plate sizes on the impinging flow field over the flat plate were investigated. Shock Mach number was varied in the range from 1.05 to 1.20. The distance between the plate and shock tube was changed to investigate the effect on the peak pressure. From both the results of experiments and computations we obtained a good empirical equation to predict the peak pressure on the flat plate.

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A Study on the Characteristics of the Pulse Wave Impinging upon a Flat Plate (평판에 충돌하는 펄스파의 특성에 관한 연구)

  • Kim, H.D.;Lee, D.H.
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.562-567
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    • 2000
  • The Impingement of a weak shock wave discharged from the open end of a shock tube upon a flat plate was investigated using shock tube experiments and numerical simulations. Harten-Yee Total Variation Diminishing method was used to solve axisymmetric, unsteady, compressible flow governing equations. Experiments were carried out to validate the present computations. The effects of the flat plate and baffle plate sizes on the impinging flow field over the flat plate were investigated. Shock Mach number was vaned in the range from 1.05 to 1.20. The distance between the plate and shock tube was changed to investigate the effect on the peak pressure. From both the results of experiments and computations we obtained a good empirical equation to predict the peak pressure on the flat plate.

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Analysis of Mixed Convection Heat Transfer in Arbitrarily Shaped Flat Tubes (임의형상을 갖는 납작관에서의 혼합대류 열전달 해석)

  • 박희용;박경우;이상철
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.5
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    • pp.398-410
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    • 2001
  • The flow and heat transfer characteristics for three-dimensional mixed convection flows in a radiator flat tube with U--shaped grooves are analyzed numerically. The flow and temperature fields are calculated by using the modified SIMPLE algorithm for irregular geometry. One tube specification among the various flat tube exchangers is recommended by considering the heat transfer and pressure drop. The effects of variation of coolant flow conditions and external air conditions on the flow and the thermal characteristics for the selected tube are investigated. the results show that inlet velocity of coolant flow is the very important factor in heat transfer and pressure drop, and top side is better position than the others as fin cleave to tube.

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Distribution of Air-Water Two-Phase Flow in a Header of Aluminum Flat Tube Evaporator (알루미늄 평판관 증발기 헤더 내 공기-물 2상류 분지 실험)

  • Kim Nae-Hyun;Shin Tae-Ryong;Sim Yong-Sup
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.1
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    • pp.55-65
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    • 2006
  • The air and water flow distribution are experimentally studied for a round header - flat tube geometry simulating a parallel flow heat exchanger. The number of branch flat tube is thirty. The effects of tube outlet direction, tube protrusion depth as well as mass flux, and quality are investigated. The flow at the header inlet is identified as annular. For the downward flow configuration, the water flow distribution is significantly affected by the tube protrusion depth. For flush-mounted configuration, most of the water flows through frontal part of the header. As the protrusion depth increases, more water is forced to the rear part of the header. The effect of mass flux or quality is qualitatively the same as that of the protrusion depth. Increase of the mass flux or quality forces the water to rear part of the header. For the upward flow configuration, however, most of the water flows through rear part of the header. The protrusion depth, mass flux, or quality does not significantly alter the flow pattern. Possible explanations are provided based on the flow visualization results. Negligible difference on the water flow distribution was observed between the parallel and the reverse flow configuration.