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1993 Fiscal Year Final Research Report Summary

Mechanism of Unsteady Flow Heat Transfer and Its Modelling

Research Project

Project/Area Number 03452129
Research Category

Grant-in-Aid for General Scientific Research (B)

Allocation TypeSingle-year Grants
Research Field Thermal engineering
Research InstitutionKYOTO UNIVERSITY

Principal Investigator

SUZUKI Kenjiro  Kyoto University, Mechanical Engineering, Professor, 工学部, 教授 (00026064)

Co-Investigator(Kenkyū-buntansha) INAOKA Kyoji  Kyoto University, Mechanical Engineering, Instructor, 工学部, 助手 (60243052)
HAGIWARA Yoshimichi  Kyoto University, Mechanical Engineering, Ass.Professor, 工学部, 助教授 (50144332)
Project Period (FY) 1991 – 1993
KeywordsUnsteady flow / Convective heat transfer / Heat transfer enhancement / Mechanism of heat transfer / Washing action / Negative production / Mpdelling
Research Abstract

Experimental study was made for an enlarged model of offset fin array to be used in heat exchagers and it reveals that, under self-sustained oscillation flow regime, one-point second-order velocity cross-correlation -uv^^- takes positive value in the wakes of fins and that its sign becomes negative around the downstream fin surface. This means that unstable flow induced in the wake is stabilized around the downstream fin and that momentum transfer is suppressed there in contranst with the heat transfer enchancement occuring at the same positions. Therefore, dissimilarity between momentum transfer and heat transfer is generated. Two-dimensional unsteady numerical computation was applied to the same type of flow of and was used to analyze the mechanism of the enchancement of fin heat transfer and of the dissimilarity between momentum and heat transfer processes. Each of counter-rotating vortices appearing in the wake entrains fresh fluid from main stream into the wake and pumps out the hot and low-speed fluid from the central part of the wake to the outside. These are effective to accelerate the recovery of the velocity defect and temperature excess int the wake. Each vortex hits the downstream fin and exerts "washing action" to the fin surface. These result in the enhancement of fin heat transfer. The washing action of each vortex produces the dissimilarity. The same numerical computation was applied to other types of flows of different geometries. In the case of channel flow obstructed by an inserted square rod, crisscross motion of Karman vortex was found. This was confirmed to actually occur through flow visualization. Unsteady flow incurred downstream of the rod enhances the wall heat transfer. The mechanism of this heat transfer enhancement is also related to the washing action of an isolated vortex produced near the wall. All these studies suggest that new idea of implementing the intermittent, washing action of vortex is important in the modelling of un

  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] 萩原良道: "タンデムフィン列およびオフセットフィン列の流動に冠する実験的研究(フィン厚さおよびフィンピッチが流れの不安定化に与える影響について)" 日本機械学会論文集. 59-560. 1222-1227 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 喜 冠南: "中間レイノルズ数域におけるフィン列の流動・伝熱特性(第1報、流れの非定常化とそれによる伝熱促進機構に対する統計的検討)" 日本機械学会論文集. 59-560. 1318-1323 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 喜 冠南: "中間レイノルズ数域におけるフィン列の流動・伝熱特性(第2報、伝熱促進機構)" 日本機械学会論文集. 59-560. 1324-1329 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] G.N.Xi: "Flow Stability and Augmented Heat Transfer of Fin Arrays" Proc.1993 ICHMT International Symposium of New Developments on Heat Exchangers. 1. 22.1-22.10 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] H.Suzuki: "Unsteady Flow in a Channel Obstructed by a Square Rod(Crisscross Motioin of Vortex)" Int.J.Heat and Fluid Flow. 14-1. 2-9 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Suzuki: "Unsteady Heat Transfer in a Channel Obstructed by an Immersed Body" Annual Review in Heat Transfer. 5. 177-206 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Y.Hagiwara: "An Experimental Study of Flow Characteristics of Offset Fin and In-Line Fin Arrays (Effects of Fin Thickness and fin Pitches on Flow Instability)" Trans.JSME B. 59-560. 1222-1227 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.N.Xi: "Flow and Heat Transfer Characteristics of Fin Arrays in the Middle Range of Reynolds Number (1st Report, Statistical Characteristics of Unsteady Flow and Temperature Fields)" Trans.JSME B. 59-560. 1318-1323 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.N.Xi: "Flow and Heat Transfer Characteristics of Fin Arrays in the Middle Range of Reynolds Number (2nd Report, Mechanism of Heat Transfer Promotion)" Trans.JSME B. 59-560. 1324-1329 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.N.Xi: "Flow Stability and Augmented Heat Transfer of fin Arrays" Proc.1993 ICHMT Int.Symp.New Developments on Heat Exchangers. 1. 22.1-22 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] H.Suzuki: "Unsteady Flow in a Channel Obstructed by a Square rod (Criss-cross Motion of Vortex)" Int.J.Heat and fluid Flow. 14-1. 2-9 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Suzuki: "Unsteady Heat Transfer in a Channel Obstructed by an Immersed Body" Annual Review of Heat Transfer. Vol.5. 177-206 (1993)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1995-03-27  

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