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Journal of Heat Transfer
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Flow Visualization and Local Measurement of Forced Convection Heat Transfer in a Microtube

J. Heat Transfer  -- March 2010 --  Volume 132,  Issue 3, 031702 (9 pages)
doi:10.1115/1.4000046

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Author(s):
Boris Schilder
Department of Mechanical Engineering, Technische Universitaet Darmstadt, Petersenstrasse 30, 64287 Darmstadt, Germany

Simon Yu Ching Man
School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore

Nobuhide Kasagi
Department of Mechanical Engineering, University of Tokyo, Tokyo 113-8656, Japan

Steffen Hardt
Center of Smart Interfaces, Technische Universitaet Darmstadt, Darmstadt D-64287, Germany

Peter Stephan
Department of Mechanical Engineering, Technische Universitaet Darmstadt, Petersenstrasse 30, 64287 Darmstadt, Germany
The pressure drop and the convective heat transfer characteristics of ethanol and water in a circular tube with a diameter of 600  µm with and without phase change have been studied experimentally. The test section consists of a glass tube coated with a transparent indium tin oxide heater film. For single-phase liquid flow (including superheated liquid) it was found that the measured Nusselt numbers and friction factors are in good agreement with the theoretical values expected from Poiseuille flow. Subsequently, the boiling heat transfer of ethanol was studied. It was found that boiling with bubble growth in both upstream and downstream directions leaving behind a thin evaporating liquid film on the tube wall is the dominant phase change process. Wavy patterns on the film surface indicate shear forces between vapor and liquid phase during slug flow. Temporary dryout phenomena occur even at a low mean vapor quality due to film rupture as a result of film instabilities. Local Nusselt numbers are calculated for the two-phase flow at different heat fluxes and Reynolds numbers. Compared with single-phase flow the heat transfer is enhanced by a factor of 3–8.

©2010 American Society of Mechanical Engineers

History: Received 20 October 2008; revised 31 July 2009; published 4 January 2010
doi: http://dx.doi.org/10.1115/1.4000046

KEYWORDS and PACS

Keywords
PACS
  • 47.80.Jk
    Flow visualization and imaging
  • 47.55.pb
    Thermal convection (nonhomogeneous flows)
  • 47.60.Dx
    Flows in ducts and channels
  • 47.55.dp
    Cavitation and boiling
  • 47.54.De
    Experimental aspects of pattern selection and formation
  • 47.85.Np
    Fluidics (applied)
  • YEAR: 2010

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PUBLICATION DATA

Coden:
JHTRAO
ISSN:
0022-1481 (print)   1528-8943 (online)
Publisher:
AIP is a member of CrossRef ASME

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