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Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Volumes per year:

various

Year 2006

DOI: 10.1615/IHTC13.p21

INSTANTANEOUS HEAT TRANSFER MEASUREMENTS BETWEEN AN UNSTEADY FLUID FLOW AND A WALL: APPLICATION TO A NON-ISOTHERMAL 2D-MIXING TEE

A. de Tilly
LET, CNRS, UMR 6608, ENSMA, 1 Avenue Clément Ader, 86961 Futuroscope, France

F. Penot
LET, CNRS, UMR 6608, ENSMA, 1 Avenue Clément Ader, 86961 Futuroscope, France

J. L. Tuhault
LET, CNRS, UMR 6608, ENSMA, 1 Avenue Clément Ader, 86961 Futuroscope, France

ABSTRACT

This article provides the description and the use of an instantaneous flux-meter. This esperiment was conducted in a non isothermal air confluence configuration where the kinematics structures and instabilities can be very specific according to the dynamical parameters. The corresponding heat flux comportments are not known, but the flow region close to the wall is influenced by the zero wall velocity condition. Therefore the normal to wall heat transfer is primarily conductive but additional terms must be added in order to take into account convective and inertial terms when it is evaluated very close to the wall layer. In this region, with air as a working fluid, the scale is thick enough to introduce a thin mesh thus allowing to calculate spatial partial derivatives. A discrete numerical scheme based on finite differences is used. According to this mesh, the disposition of four thin temperature wires leads to estimate the spatial and temporal partial derivatives of the zero and first orders. The mean and fluctuating heat fluxes can be deducted from the turbulent convective temperature equations. In the air confluence's prototype, the instabilities encountered (Kelvin-Helmholtz rolls, pulse valve effect and turbulent flapping) are briefly described. The obtained temporal and spatial flux distribution levels are found qualitatively equivalent to the kinematics patterns of the flow. These results are relevant in the research domain regarding thermal and dynamical phenomena leading to thermal stripping.