Effects of operating frequency of a synthetic jet and cross flow velocity on the heat transfer enhancement in a micro-channel

Mark E. Zschirnt, Ann Lee*, Guan H. Yeoh

*Corresponding author for this work

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

1 Citation (Scopus)

Abstract

Current devices have been reported to approach 1 MW/m2 so that current heat dissipation devices will not be able to cope with increasing heat flux. It has therefore been proposed that in order to manage the ever-increasing heat rejection demands, it will be necessary to have cooling fluid flowing through microchannels in the microchip itself. Since laminar flow is likely to result for reasonable pressure drops in these micro-channels, the heat transfer rate will need to be enhanced if this approach is to be successfully used. Synthetic jets, which are the main focus of this research, generate vortex structures which disrupt the flow. They have, therefore, been proposed as a means of providing mixing, thereby augmenting the heat transfer potential of the fluid in the micro-channel. A two-dimensional computational model has been developed to investigate the cooling effect of a synthetic jet interacting with a turbulent cross-flow in a micro-channel. Validation of the hydrodynamics feature of the flow was done by comparing numerical results against existing experimental results. A parametric study was performed on a fixed geometry by using a constant wall temperature to investigate the effect of operating frequency of the synthetic jet actuator coupling with different flow rates in the micro-channel. The operating frequencies of the jet were simulated at 1000 Hz, 1500 Hz and 2000 Hz while the cross flows vary from 0 to 10 m/s. In general, the flow structures in the micro-channel were shown to be greatly disrupted when the synthetic jet actuator was turned on. However, the heat transfer enhancement due to the operation of the synthetic jet reduces as the cross flow increases. The frequency of the diaphragm oscillation has a large influence on the distance between the adjacent vortices and therefore on the average flow rate in the micro-channel. The near wall Nusselt Number was calculated in order to compare the effects of operating frequency of the jet and flow rate in the micro-channel. The jet Reynolds number was increased by 50% when the actuator frequency was increased from 1000 Hz to 1500 Hz while the heat transfer enhancement was increased by 21%. Further increment of actuator frequency from 1000 Hz to 2000 Hz resulted in a doubled jet Reynolds number while the heat transfer enhancement was improved by 66%. The heat transfer enhancement showed greater improvement when the actuator operating at 2000 Hz.

Original languageEnglish
Title of host publicationASME 2013 Fluids Engineering Division Summer Meeting, FEDSM 2013
Place of PublicationNew York
PublisherASME
Pages1-10
Number of pages10
Volume2
ISBN (Print)9780791855584
DOIs
Publication statusPublished - 2013
Externally publishedYes
EventASME 2013 Fluids Engineering Division Summer Meeting, FEDSM 2013 - Incline Village, NV, United States
Duration: 7 Jul 201311 Jul 2013

Other

OtherASME 2013 Fluids Engineering Division Summer Meeting, FEDSM 2013
CountryUnited States
CityIncline Village, NV
Period7/07/1311/07/13

Keywords

  • Heat transfer enhancement
  • Micro-channel
  • Numerical modeling
  • Synthetic jet

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  • Cite this

    Zschirnt, M. E., Lee, A., & Yeoh, G. H. (2013). Effects of operating frequency of a synthetic jet and cross flow velocity on the heat transfer enhancement in a micro-channel. In ASME 2013 Fluids Engineering Division Summer Meeting, FEDSM 2013 (Vol. 2, pp. 1-10). [V002T21A002] New York: ASME. https://doi.org/10.1115/FEDSM2013-16028