Effect of Pressure with Wall Heating in Annular Two-Phase Flow

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The local distributions of void fraction, interfacial frequency and velocity have been measured in annular flow of R-134a through a wall-heated, high aspect ratio duct. High aspect ratio ducts provide superior optical access to tubes or irregular geometries. This work expands upon earlier experiments conducted with adiabatic flows in the same test section. Use of thin, transparent heater films on quartz windows provided sufficient electrical power capacity to produce the full range of two-phase conditions of interest. With wall vapor generation, the system pressure was varied from 0.9 to 2.4 MPa, thus allowing the investigation of flows with liquid-to-vapor density ... continued below

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1164 Kilobytes pages

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Kumar, R. & Trabold, T.A. October 31, 2000.

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  • Lockheed Martin
    Publisher Info: Lockheed Martin Corporation, Schenectady, NY 12301 (United States)
    Place of Publication: Schenectady, New York

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Description

The local distributions of void fraction, interfacial frequency and velocity have been measured in annular flow of R-134a through a wall-heated, high aspect ratio duct. High aspect ratio ducts provide superior optical access to tubes or irregular geometries. This work expands upon earlier experiments conducted with adiabatic flows in the same test section. Use of thin, transparent heater films on quartz windows provided sufficient electrical power capacity to produce the full range of two-phase conditions of interest. With wall vapor generation, the system pressure was varied from 0.9 to 2.4 MPa, thus allowing the investigation of flows with liquid-to-vapor density ratios covering the range of about 7 to 27, far less than studied in air-water and similar systems. There is evidence that for a given cross-sectional average void fraction, the local phase distributions can be different depending on whether the vapor phase is generated at the wall, or upstream of the test section inlet. In wall-heated flows, local void fraction profiles measured across both the wide and narrow test section dimensions illustrate the profound effect that pressure has on the local flow structure; notably, increasing pressure appears to thin the wall-bounded liquid films and redistribute liquid toward the edges of the test section. This general trend is also manifested in the distributions of mean droplet diameter and interfacial area density, which are inferred from local measurements of void fraction, droplet frequency and velocity. At high pressure, the interfacial area density is increased due to the significant enhancement in droplet concentration.

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1164 Kilobytes pages

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OSTI as DE00821307

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  • Other Information: PBD: 31 Oct 2000

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  • Report No.: LM-00K074
  • Grant Number: AC12-00SN39357
  • DOI: 10.2172/821307 | External Link
  • Office of Scientific & Technical Information Report Number: 821307
  • Archival Resource Key: ark:/67531/metadc734378

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  • October 31, 2000

Added to The UNT Digital Library

  • Oct. 18, 2015, 6:40 p.m.

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  • April 28, 2016, 8:43 p.m.

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Kumar, R. & Trabold, T.A. Effect of Pressure with Wall Heating in Annular Two-Phase Flow, report, October 31, 2000; Schenectady, New York. (digital.library.unt.edu/ark:/67531/metadc734378/: accessed May 26, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.