Agitation is produced inside a channel by a plate that is periodically oscillating normal to the channel side walls. The test channel is a rectangular cavity open on one end to allow inflow and outflow of air, as driven by the plate movement. Heat transfer and velocity measurements are made within different regions of the channel to study the effectiveness of agitation in promoting heat transfer from the channel side wall. The purpose of agitation is to strongly mix the near-wall flow, to thin the thermal boundary layer and increase the convective heat transfer coefficient. Velocity measurements using laser Doppler velocimetry are made to document the fluctuations of velocity within the agitated cavity. Variations of ensemble-averaged velocity throughout the cycle identify the unsteady sloshing of the flow. Cycle-to-cycle variations about the ensemble mean computed as an RMS and resolved in time within the cycle period present the changing turbulence levels throughout the agitation cycle. The ensemble-averaged mean velocity variations show periods of acceleration, deceleration and flow reversal during a cycle as a result of agitator movement. Turbulence is found to increase toward the end of the acceleration phase and persist through the deceleration phase. Intensities of sloshing and turbulence are used to explain the measured convective heat transfer coefficients. ANSYS FLUENT simulations supply velocity contours and flow visualization. This study finds application in electronics cooling where agitation can be used inside air-cooled heat sinks to enhance heat transfer to through-flow driven by a fan.
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ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels
July 8–12, 2012
Rio Grande, Puerto Rico, USA
Conference Sponsors:
- Heat Transfer Division
ISBN:
978-0-7918-4478-6
PROCEEDINGS PAPER
An Experimental Study on the Effects of Agitation in Generating Flow Unsteadiness and Enhancing Convective Heat Transfer
Smita Agrawal,
Smita Agrawal
University of Minnesota, Minneapolis, MN
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Terrence Simon,
Terrence Simon
University of Minnesota, Minneapolis, MN
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Tianhong Cui
Tianhong Cui
University of Minnesota, Minneapolis, MN
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Smita Agrawal
University of Minnesota, Minneapolis, MN
Terrence Simon
University of Minnesota, Minneapolis, MN
Mark North
Thermacore Inc., Lancaster, PA
Tianhong Cui
University of Minnesota, Minneapolis, MN
Paper No:
HT2012-58273, pp. 649-657; 9 pages
Published Online:
July 24, 2013
Citation
Agrawal, S, Simon, T, North, M, & Cui, T. "An Experimental Study on the Effects of Agitation in Generating Flow Unsteadiness and Enhancing Convective Heat Transfer." Proceedings of the ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. Volume 2: Heat Transfer Enhancement for Practical Applications; Fire and Combustion; Multi-Phase Systems; Heat Transfer in Electronic Equipment; Low Temperature Heat Transfer; Computational Heat Transfer. Rio Grande, Puerto Rico, USA. July 8–12, 2012. pp. 649-657. ASME. https://doi.org/10.1115/HT2012-58273
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