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ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

EXPERIMENTAL STUDIES ON FLOW VISUALIZATION AND HEAT TRANSFER CHARACTERISTICS IN MICROTUBES

Get access (open in a dialog) DOI: 10.1615/IHTC13.p14.120
12 pages

Résumé

Flow visualization and friction as well as heat transfer characteristics in microtubes are investigated experimentally in this paper. The working fluids are water, ethanol and tetra chloromethane flowing through smooth quartz glass microtubes and rough stainless steel microtubes with inner diameters 168∼799μm. The relationship between the friction factor and Reynolds number is obtained by measuring the pressure drop and the flow rate. Meanwhile, the flow field pictures in quartz glass microtube are shot by a CCD camera with a microscope as distilled water is used as the working fluid and gentian violet is used as a colorant. The heat transfer coefficients in stainless steel microtubes are obtained based on the measurement of tube wall temperature by using an IR camera. The experimental results clearly show that the flow in microtube is laminar state and the friction factors agree well with the Poiseuille equations when Reynolds number is low. As Reynolds number is larger than 1100∼1500 for the smooth microtubes, the friction factor departs from the classical laminar solution due to the earlier transition from laminar to turbulent flow, and the flow turns into turbulent when Reynolds number reaches 1500∼1800. For the rough stainless steel microtube with 8% relative roughness, the friction factor is larger than the Poiseuille equations when Reynolds number exceeds about 800, and the Nusselt number dramatically increases when Reynolds number exceeds 650∼800, so the results of heat transfer also show the earlier transition of flow.