Unsteady heat transfer around low aspect ratio cylinders in an array

Shawn Siroka, Melissa Shallcross, Stephen Lynch

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

Cylindrical pins, often called pin fins, are used to create turbulence and promote convective heat transfer within many devices, ranging from computer heat sinks to the trailing edge of jet engine turbine blades. Previous experiments have measured the time-averaged heat transfer over a single pin as well as the flow fields around the pin. However, in this study, focus is placed on the instantaneous heat flux around the centerline of a low aspect-ratio pin within an array. Time-mean and unsteady convective heat flux are measured around the circumference of an isothermal heated test pin via a microsensor located at the surface. The pin is positioned at various locations within a staggered array in a large-scale wind tunnel. Reynolds numbers from 3,000 to 50,000, based on pin diameter and maximum velocity between pins, are tested with a streamwise spacing of 1.73 diameters between rows, a spanwise spacing of 2 diameters, and a pin height of 1 diameter. The time-averaged and standard deviation of convective heat flux around the pin is higher over most of the pin surface for pins in downstream row positions of an array relative to the first row pin, except in the wake which has similar levels for all rows. For a given pin position in the array, as the Reynolds number increases, the point of minimum heat transfer moves circumferentially upstream on the pin fin, corresponding to earlier transition of the pin boundary layer. Also, for a given Reynolds number, the minimum heat transfer point on the pin circumference moves upstream for pins further into the array, due to the high turbulence levels within the array which cause early transition. For a single pin row with no downstream pins, heat transfer fluctuations are very high on the backside of the pin due to the significant unsteadiness in the pin wake, but heat transfer fluctuations are suppressed for a pin with downstream rows due to the confining effects of the close spacing. The results from this study can be used to design pinfin arrays that take advantage of unsteadiness and increase overall convective heat transfer for various industry components.

Original languageEnglish (US)
Title of host publicationHeat Transfer and Thermal Engineering
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791850626
DOIs
StatePublished - Jan 1 2016
EventASME 2016 International Mechanical Engineering Congress and Exposition, IMECE 2016 - Phoenix, United States
Duration: Nov 11 2016Nov 17 2016

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Volume8

Other

OtherASME 2016 International Mechanical Engineering Congress and Exposition, IMECE 2016
CountryUnited States
CityPhoenix
Period11/11/1611/17/16

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering

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  • Cite this

    Siroka, S., Shallcross, M., & Lynch, S. (2016). Unsteady heat transfer around low aspect ratio cylinders in an array. In Heat Transfer and Thermal Engineering (ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE); Vol. 8). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/IMECE201666783