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HEAT TRANSFER IN NANOCHANNELS, MICROCHANNELS, AND MINICHANNELS

Numerical Investigation of Heat Transfer in Rectangular Microchannels Under H2 Boundary Condition During Developing and Fully Developed Laminar Flow

[+] Author and Article Information
V. V. Dharaiya

S. G. Kandlikar

Thermal Analysis, Microfluidics and Fuel Cell Laboratory, Rochester Institute of Technology, Rochester, NY 14623, USAsgkeme@rit.edu

J. Heat Transfer 134(2), 020911 (Dec 22, 2011) (10 pages) doi:10.1115/1.4004934 History: Received December 22, 2010; Revised June 23, 2011; Published December 22, 2011; Online December 22, 2011

Study of fluid flow characteristics at microscale is gaining importance with shrinking device sizes. Better understanding of fluid flow and heat transfer in microchannels will have important implications in electronic chip cooling, heat exchangers, MEMS, and microfluidic devices. Due to short lengths employed in microchannels, entrance header effects can be significant and need to be investigated. In this work, three dimensional model of microchannels, with aspect ratios (α = a/b) ranging from 0.1 to 10, are numerically simulated using CFD software tool fluent . Heat transfer effects in the entrance region of microchannel are presented by plotting average Nusselt number as a function of nondimensional axial length x*. The numerical simulations with both circumferential and axial uniform heat flux (H2) boundary conditions are validated for existing data set for four wall heat flux case. Large numerical data sets are generated in this work for rectangular cross-sectional microchannels with heating on three walls, two opposing walls, one wall, and two adjacent walls under H2 boundary condition. This information can provide better understanding and insight into the transport processes in the microchannels. Although the results are seen as relevant in microscale applications, they are applicable to any sized channels. Based on the numerical results obtained for the whole range, generalized correlations for Nusselt numbers as a function of channel aspect ratio are presented for all the cases. The predicted correlations for Nusselt numbers can be very useful resource for the design and optimization of microchannel heat sinks and other microfluidic devices.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 13

Rectangular ducts: NuH2,fd for fully developed laminar flow and for one or more walls transferring heat under uniform heat flux H2 boundary condition

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Figure 12

Local Nusselt number as a function of nondimensional length and channel aspect ratio for one-wall H2 boundary condition

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Figure 11

Local Nusselt number as a function of nondimensional length and channel aspect ratio for two opposite wall H2 boundary condition

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Figure 10

Local Nusselt number as a function of nondimensional length and channel aspect ratio for three-wall H2 boundary condition

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Figure 9

Plot of Nu along the length of the rectangular microchannel having smooth and abrupt entrance with H2 boundary conditon on three walls

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Figure 8

Plot of Nu along the length of the rectangular microchannel having smooth and abrupt entrance with H2 boundary conditon on four walls

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Figure 7

For rectangular ducts—fully developed laminar flow Nusselt numbers for NuT , NuH1 , and NuH2 and validation of numerical model used

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Figure 6

Schematic and meshing of geometric model with smooth entrance type

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Figure 5

Schematic and meshing of geometric model with abrupt entrance type

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Figure 4

Temperature variation along the height of a rectangular microchannel for 0.5 aspect ratio

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Figure 3

Temperature variation along the width of a rectangular microchannel for 0.5 aspect ratio

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Figure 2

Cross-sectional area of rectangular microchannel with H2 boundary condition on 4-walls for 0.5 aspect ratio (channel width—300 μm and channel height—150 μm)

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Figure 1

Cross-sectional area of rectangular microchannel with uniform heat flux on all four walls

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