Title

The effect of freestream turbulence on convection enhancement by a flexible strip

Document Type

Article

Publication Date

5-1-2021

Publication Title

Experimental Thermal and Fluid Science

Volume

123

Keywords

Flexible strip, Freestream turbulence, Heat transfer enhancement

Abstract

Turbulence generators such as a 25.4 mm tall, 12.7 mm wide (W) and 0.1 mm thick rectangular flexible strip can provide a robust means of enhancing convective heat transfer. This wind-tunnel study aimed at uncovering the effect of freestream turbulence on heat convection enhancement of a flat surface by a flexible strip. The freestream turbulence was furnished by a 6 mm thick orificed perforated plate (OPP) with 57% perforation consisting of 38.1 mm diameter (D) holes. The OPP was installed at 10D, 13D and 16D upstream of the strip, to achieve 11%, 9% and 7% turbulence. The investigation was conducted at a Reynolds number based on the strip width of 6000. The convective heat transfer augmentation was analyzed in terms of Nusselt number with respect to the reference no-strip case (Nu/Nu0). The flow turbulence was characterized with the help of a 3D hotwire probe. The freestream turbulence is found to diminish the flexible-strip induced Nu/Nu0 significantly. This is principally because Nu0 increases considerably with increasing freestream turbulence. It is of practical significance that the flexible strip always increases Nu, and this improvement is largest with respect to an otherwise ‘laminar’ freestream.

DOI

10.1016/j.expthermflusci.2020.110345

ISSN

08941777

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