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Investigation of the influence of free convection on the heat transfer of cylinders with different aspect ratios

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Abstract

Electrically heated cylindrical wires are used in research and industry for fluid velocity and turbulence measurements. At very low free-stream velocities (u≤0.1 m/s), hot-wire measurements are significantly influenced by buoyant convection. Below a certain Reynolds number Re* this effect degrades the accuracy of the measurements. To assess the contribution of free-convection heat transfer to the heat balance of hot-wires in cross flow, measurements under normal gravity and microgravity (µg) conditions are compared keeping all other parameters constant. Under gravity conditions, the acceleration of gravity, the hot-wire axis and the direction of the free stream are all perpendicular to each other. The microgravity experiments were carried out in the Drop-Tower Bremen in which the residual acceleration is less than 10−5 g during a period of 4.7 s. The present investigation is concerned with a velocity range of 0≤u≤0.35 m/s corresponding to a Reynolds number range Re<0.1 in standard air. This range includes pure free convection for Re→0 and forced-convection-dominated heat transfer for Re=0.1. At intermediate Reynolds numbers both transport mechanisms must be considered.

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Authors and Affiliations

  1. ZARM - University of Bremen, 28359, Bremen, Germany

    C. Henselowsky & H. C. Kuhlmann

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  1. C. Henselowsky
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  2. H. C. Kuhlmann
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  3. H. J. Rath
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Correspondence to C. Henselowsky.

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Henselowsky, C., Kuhlmann, H.C. & Rath, H.J. Investigation of the influence of free convection on the heat transfer of cylinders with different aspect ratios. Microgravity sci. Technol. 13, 43 (2002). https://doi.org/10.1007/BF02872076

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  • DOI: https://doi.org/10.1007/BF02872076

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