RESEARCH PAPERS: Heat Transfer Enhancement

Heat Transfer Augmentation by Ion Injection in an Annular Duct

[+] Author and Article Information
Walter Grassi

 LOTHAR (LOw gravity and THermal Advanced Research Laboratory), Department of Energetics, “L. Poggi,” University of Pisa, via Diotisalvi 2, 56126 Pisa, Italyw.grassi@ing.unipi.it

Daniele Testi

 LOTHAR (LOw gravity and THermal Advanced Research Laboratory), Department of Energetics, “L. Poggi,” University of Pisa, via Diotisalvi 2, 56126 Pisa, Italyd.testi@ing.unipi.it

J. Heat Transfer 128(3), 283-289 (Aug 23, 2005) (7 pages) doi:10.1115/1.2150838 History: Received January 21, 2005; Revised August 23, 2005

The thermofluid-dynamic effects of ion injection from sharp metallic points added perpendicularly to the inner wire of a short horizontal annulus were experimentally investigated. A dielectric liquid (FC-72 by 3M) was weakly forced to flow in the duct, which was uniformly heated on the outer wall. A dc voltage as high as 22kV was applied to the inner electrode, while the heated wall was grounded. Both the laminar and the turbulent mixed-convection regimes were obtained, varying the imposed flow rate. Once an electric field is applied, the flow is dramatically modified by the jets of charged particles, which transfer their momentum to the neutral adjacent ones. Different injection strengths were obtained on the emitters, because the shape of the point tips was not controlled at the microscale. Nusselt number distributions were obtained azimuthally and longitudinally, monitoring the wall temperatures. In all cases, heat transfer turned out greatly enhanced in the proximity of the emitters, without a significant increase in pressure drop through the test section and with a negligible Joule heating, making this technique very attractive for application in compact heat exchangers.

Copyright © 2006 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Figure 1

Schematic of the test loop

Grahic Jump Location
Figure 2

Detail of the EHD test section

Grahic Jump Location
Figure 3

Position of the points in configuration 2

Grahic Jump Location
Figure 4

Nu distribution at Re=2220 and Grh=1.40×108

Grahic Jump Location
Figure 5

Drawing of the microasperities at the point tip

Grahic Jump Location
Figure 6

Presumed dynamics of the jets from the points in configuration 1

Grahic Jump Location
Figure 7

Nu distribution at Re=740 and Grh=1.40×108

Grahic Jump Location
Figure 8

Nu vs ξ at Re=2220 and Grh=1.40×108 and Grh=2.47×108 (dotted curves)

Grahic Jump Location
Figure 9

⟨Nu⟩ vs ξ at Grh=1.40×108

Grahic Jump Location
Figure 10

⟨Nu⟩ vs ξ in vertical aiding flow at Grh=3.89×108(3)

Grahic Jump Location
Figure 11

⟨Nu⟩ vs Re (Secs. B and D) at Grh=1.40×108




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In