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International Heat Transfer Conference 13

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

PIV MEASUREMENT OF THE FLOW FIELD IN A SQUARE CHANNEL WITH PERIODIC TRANSVERSE RIBS ON ONE WALL

Lieke Wang
Division of Heat Transfer Lund Institute of Technology Box 118, 221 00, Lund Sweden; Siemens Industrial Turbomachinery AB, Finspong, SE-61283, SWEDEN

Jiri Hejcik
Brno University of Technology, Brno, Czech Republic

Bengt Sunden
Division of Heat Transfer, Department of Energy Sciences, Lund University, P.O. Box 118, SE-22100, Lund, Sweden

DOI: 10.1615/IHTC13.p21.40
11 pages

要約

In this study, Particle Image Velocimetry (PIV) is used to investigate the flow structure of separated flow in a square channel roughened with periodically transverse ribs on one wall; meanwhile, the detailed heat transfer coefficient distribution between two adjacent ribs, which is the time-averaged influence of unsteady flow structure on the thermal field, is obtained by Liquid Crystal Thermography (LCT). The ribs obstruct the channel by 15% of its height and are arranged 12 rib heights apart. The Reynolds number, based on the channel hydraulic diameter and the freestream bulk velocity, is fixed at 20,000. It is found that the heat transfer and turbulent fluctuation reach their maximum value in the vicinity of the reattachment point (line). The negative vertical velocity component, which leads to the entrainment of cold fluid from the shear layer, causes the increase of heat transfer in the recirculating region. The time-average reattachment length measured by LCT is in agreement with the result of PIV. However, the instantaneous reverse-flow length, otherwise constant, is observed elongating and shrinking in the streamwise direction on account of the flapping motion of the separated shear layer. Downstream the reattachment point, the redeveloping is not in local energy equilibrium. The mixture length measured at x/e = 8 is greater than the length scale proposed by Prandtl, which indicates that larger energetic eddies still exist in the redevelopment region.

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Measurement of fluid temperature with an arrangement of three thermocouples