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TECHNICAL PAPERS: Micro/Nanoscale Heat Transfer

Analysis of Thermally Expandable Flexible Fluidic Thin-Film Channels

[+] Author and Article Information
A.-R. A. Khaled

Thermal Engineering and Desalination Technology Department, King AbdulAziz University, Jeddah, 21589, Saudi Arabia

K. Vafai1

Department of Mechanical Engineering, University of California, Riverside, Riverside, CA 92521

1

Corresponding author.

J. Heat Transfer 129(7), 813-818 (Oct 02, 2006) (6 pages) doi:10.1115/1.2712853 History: Received March 15, 2006; Revised October 02, 2006

Heat transfer inside thermally expandable and flexible fluidic thin-film channels is analyzed in this work. Two categories are analyzed: the first category is when the upper plate of the thin film is mobile and flexible, and the second is when the side plates of the thin film are flexible and mobile. The expansion in the thin-film heights (category I) or widths (category II) are linearly related to the local fluid pressure and the local temperature of the heated plate based on the principles of linear elasticity and constant volumetric thermal expansion coefficient. The governing Reynolds, momentum, and energy equations are properly nondimensionalized and solved numerically using an implicit method. The Peclet number, stiffness parameter, thermal expansion parameter, and aspect ratio are found to be the main controlling parameters. It is found that thermally expandable flexible thin films that belong to category I can produce significant increase in cooling as the heating load increases, especially when operated at lower Peclet numbers, whereas the cooling effect for those that belong to category II is almost unaffected by the expansion. This work paves the way to practically utilize thermally expandable flexible thin films, especially in MEMS and electronic cooling applications.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Thermally expandable flexible thin film with mobile flexible upper plate (category I) and (b) Thermally expandable flexible thin film with mobile flexible side plates (category II)

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Figure 2

Variation of the dimensionless thin film height H with the thermal expansion parameter FT1 (category I)

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Figure 3

Variation of the dimensionless mean bulk temperature θm and dimensionless lower plate temperature θB with the thermal expansion parameter FT1 (category I)

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Figure 4

Variation of the dimensionless thin film height H with Peε (category I)

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Figure 5

Variation of the dimensionless mean bulk temperature θm and dimensionless lower plate temperature θB with Peε (category I)

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Figure 6

Variation of the lower plate temperature at the exit θB(FT1,X=1) relative to that when FT1=0 with Peε and FT1 (category I)

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Figure 7

Variation of the average Nusselt number Nuavg(FT1,X=1) relative to that when FT1=0 with Peε and FT1 (category I)

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Figure 8

Variation of the dimensionless thin film width D¯ with the thermal expansion parameter FT2 (category II)

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Figure 9

Variation of the dimensionless mean bulk temperature θm and dimensionless lower plate temperature θW with the thermal expansion parameter FT2 (category II)

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