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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

SIMULTANEOUS MEASUREMENTS OF THE THERMAL AND VELOCITY BOUNDARY LAYER OVER A HEATED FLAT PLATE USING THERMOGRAPHIC LASER DOPPLER VELOCIMETRY

Get access (open in a dialog) DOI: 10.1615/IHTC16.tpm.023986
pages 8775-8780

Abstract

We present the first application of thermographic phosphor tracer particles for simultaneous measurements of the thermal and velocity boundary layers over a heated flat plate. To accomplish these measurements, we employed the recently developed thermographic laser Doppler velocimetry (thermographic LDV) technique using micron-size BaMgAl10O17:Eu2+ (BAM:Eu2+) phosphor particles as flow tracers. With this point-based measurement technique, the flow velocity is determined from the frequency of the scattered laser light when individual phosphor particles traverse the fringes of two crossed visible laser beams as in conventional LDV. Upon excitation of the same phosphor particles by a focused continuous wave UV laser beam that overlapped the LDV measurement volume, the temperature-dependent luminescence emission from the particles is simultaneously detected. Flow temperature is evaluated from these acquired luminescence signals using a two-colour intensity ratio method. In this study, combined temperature and velocity measurements were performed in the boundary layer of room temperature air flow over a heated flat plate as close as 200 μm from the heated surface. The temperature measurements show an excellent agreement (2 K (0.63 %) mean deviation) with the solution of the boundary layer energy equation based on the measured velocity profile demonstrating a negligible interference from light scattered or reflected off the wall. The thermographic LDV sensor is a suitable tool for near-wall measurements of shear flows in heat transfer research.