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2003 Fiscal Year Final Research Report Summary

BASIC STUDIES ON THE DEVELOPMENT OF HIGHLY EFFICIENT COMPACT HEAT EXCHANGER WITH LOW ENVIRONMENTAL LOAD

Research Project

Project/Area Number 14550181
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Thermal engineering
Research InstitutionKYOTO INSTITUTE OF TECHNOLOGY

Principal Investigator

HAGIWARA Yoshimichi  KYOTO INSTITUTE OF TECHNOLOGY, FACULTY OF ENGINEERING AND DESIGN, PROFESSOR, 工芸学部, 教授 (50144332)

Co-Investigator(Kenkyū-buntansha) TANAKA Mitsuru  KYOTO INSTITUTE OF TECHNOLOGY, FACULTY OF ENGINEERING AND DESIGN, ASSOCIATE PROFESSOR, 工芸学部, 助教授 (20281115)
Project Period (FY) 2002 – 2003
Keywordsliquid-liquid direct contact / high-density inactive liquid / upward water flow / PLIF / PTV / direct numerical simulation / near-wall turbulence structure / local heat transfer
Research Abstract

The experiments were conducted for the upward water flow in a vertical pipe with falling immiscible droplets of hydrofluoroether (HFE-7200) or perfluorocarbon (FC-72). The visualization of velocity field and temperature field and image processing were carried out.
(1) The HFE-7200 droplets fall with noticeable wobbling in the near-wall region of the turbulent upward water flow. On the other hand, the droplets whose specific weight is higher than that of hFE-7200 fall with small-amplitude wobbling in the central region. The increases in the turbulence intensities and the decrease in the mean velocity are measured in the region of droplet passing. The vortices in the wake flow of the droplets cause the change in the turbulence statistics. The outward or wallward flow induced by the flow of HFE-7200 droplets affects the near-wall coherent structure.
(2) The Strouhal number for the droplet motion can be estimated from the empirical of rising bubbles. This Strouhal number is lower than the St … More rouhal number of vortex shedding from a solid sphere.
(3) The circular fluid motion was observed in the wake flow region. This motion is considered to be the cross sections of the unsteady Ω-shaped vortex tube. The thermal wake region is smaller than the area of passing the Ω-shaped vortex tube in the wake flow. This is because the Prandtl number is high and because high-temperature fluid outside the tube was carried into the wake flow region surrounded by vortex tube.
(4) The high velocity flow in the wall jet between the funnel and the pipe inner wall decelerated the droplet falling velocity. The droplet was easily transported in the central region by the wall-normal fluctuating velocity generated by the tripping wire. The funnel and tripping wire allocated near the bottom of the test section worked well for collecting all the descent droplets.
The direct numerical simulation was carried out for turbulent upward flow between two heating walls with four immiscible droplets. The main conclusions obtained are as follows.
(1) The droplet induced several types of secondary flows. These flows increased the Reynolds shear stress product. These flows were attenuated by the adjacent in the streamwise direction. The small-scale streamwise vortices were attenuated near the droplets. The large-scale developed streamwise vortices were deformed by the droplets.
(2) The product of wall-normal velocity fluctuation and the temperature fluctuation increased by the secondary flows. This shows an enhancement of turbulent heat transfer by droplets. Less

  • Research Products

    (10 results)

All Other

All Publications (10 results)

  • [Publications] Y.Hagiwara, T.Yuge, S.Takagaki: "Heat Transfer Enhancement by an Immiscible Droplet Wobbling in Near-wall Region of Turbulent Downward Liquid Flow"J.of Enhanced Heat Transfer. Vol.10. 81-93 (2003)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Yuge, Y.Hagiwara: "The Modifications of Near-wall Turbulence Structure and Heat Transfer by Immiscible Droplets in Turbulent Liquid-liquid Two-phase Flow"Int.J.Heat and Fluid Flow. Vol.25(in print). (2004)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Y.Hagiwara, T.Suzaki, D.Saegusa: "Interaction between Near-wall Turbulence Structure and Immiscible Droplets Falling with Wobbling Motion in Upward Water Flow"Int.J.of Energy. Vol.29(to appear). (2004)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] M.Goto, N.Matsukura, Y.Hagiwara: "Heat Transfer Characteristics of Warm Water Flow with Cool Immiscible Droplets in a Vertical Pipe"Experimental Thermal and Fluid Science. Vol.28(to appear). (2004)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Tajima, N.Matsukura, M.Tanaka, Y.Hagiwara: "Control of Droplet Motion by Wall Jet and a Turbulence Promoter in Turbulent Dispersed Liquid-liquid Two-phase Flow in a Pipe"Turbulence, Heat and Mass Transfer 4 (ed.by K.Hanjalic, Y.Nagano, M.J.Tummers), Begell House Inc.. 1031-1038 (2003)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Hagiwara Y., Takagaki S., Yuge T.: "Effects of a droplet on near-wall transport phenomena in turbulent downward liquid-liquid flow"J. Enhanced Heat Transfer. Vol.10. 81-93 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Yuge T., Hagiwara Y.: "The modifications of near-wall turbulence structure and heat transfer by immiscible droplets in turbulent liquid-liquid two-phase flow"Int. J. Heat and Fluid Flow. Vol.25 (in press). (2004)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Hagiwara Y., Suzaki T., Saegusa D.: "Interaction between near-wall turbulence structure and immiscible droplets falling with wobbling motion in upward water flow"Int. J. of Energy. Vol.29 (to appear). (2004)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Goto M., Matsukura N., Hagiwara Y.: "Heat transfer characteristics of warm water flow with cool immiscible droplets in a vertical duct"Experimental Thermal and Fluid Science. Vol.28 (to appear). (2004)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Tajima M., Matsukura N., Tanaka M., Hagiwara Y.: "Control of droplet motion by wall jet and turbulence promoter in turbulent dispersed liquid-liquid two-phase flow in a pipe"Turbulence, Heat and Mass Transfer 4 (ed. by K.Hanjalic, Y. Nagano, M. J. Tummers) (Begell House, Inc.). 1031-1038 (2003)

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

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Published: 2005-04-19  

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