0
Research Papers: Micro/Nanoscale Heat Transfer

Viscous Dissipation and Rarefaction Effects on Laminar Forced Convection in Microchannels

[+] Author and Article Information
Arman Sadeghi

Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, P.O. Box 11155-9567, Tehran, Iran

Mohammad Hassan Saidi1

Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, P.O. Box 11155-9567, Tehran, Iransaman@sharif.edu

1

Corresponding author.

J. Heat Transfer 132(7), 072401 (Apr 22, 2010) (12 pages) doi:10.1115/1.4001100 History: Received January 31, 2009; Revised January 12, 2010; Published April 22, 2010; Online April 22, 2010

Fluid flow in microchannels has some characteristics, which one of them is rarefaction effect related with gas flow. In the present work, hydrodynamically and thermally fully developed laminar forced convection heat transfer of a rarefied gas flow in two microgeometries is studied, namely, microannulus and parallel plate microchannel. The rarefaction effects are taken into consideration using first-order slip velocity and temperature jump boundary conditions. Viscous heating is also included for either the wall heating or the wall cooling case. Closed form expressions are obtained for dimensionless temperature distribution and Nusselt number. The results demonstrate that for both geometries, as Brinkman number increases, the Nusselt number decreases. However, the effect of viscous heating on the Nusselt number at greater values of Knudsen number becomes insignificant. In the absence of viscous heating, increasing values of Knudsen number lead to smaller values of Nusselt number. Furthermore, it is observed that viscous heating causes singularities in Nusselt number values. Also, asymmetry causes singularities in Nusselt numbers of both microannulus walls and the parallel plate wall having lower heat flux, even in the absence of viscous heating. For parallel plate microchannel, in the absence of viscous heating, Nusselt number of the wall having larger heat flux is an increasing function of the wall heat fluxes ratio.

FIGURES IN THIS ARTICLE
<>
Copyright © 2010 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 14

Nusselt number values of microannulus versus β at different values of η (a) inner wall and (b) outer wall

Grahic Jump Location
Figure 13

Nusselt number values of microannulus versus β at different Knudsen numbers (a) inner wall and (b) outer wall

Grahic Jump Location
Figure 12

Brinkman number dependency of microannulus Nusselt numbers at different values of η (a) inner wall and (b) outer wall

Grahic Jump Location
Figure 11

Nusselt number values of parallel plate microchannel versus η at different Knudsen numbers (a) upper wall and (b) lower wall

Grahic Jump Location
Figure 10

Nusselt number values of microannulus versus η at different Knudsen numbers (a) inner wall and (b) outer wall

Grahic Jump Location
Figure 9

Nusselt number values of the upper wall versus Knudsen number at different Brinkman numbers for parallel plate microchannel (a) η=0 and (b) η=1

Grahic Jump Location
Figure 8

Nusselt number values of the microannulus inner wall versus Knudsen number at different Brinkman numbers (a) η=0 and (b) η=1

Grahic Jump Location
Figure 1

Geometries of the ducts (a) microannulus and (b) parallel plate microchannel

Grahic Jump Location
Figure 7

Rarefaction effects on dimensionless temperature profile for parallel plate microchannel

Grahic Jump Location
Figure 6

Rarefaction effects on dimensionless temperature profile for microannulus with β=0.5

Grahic Jump Location
Figure 5

Rarefaction effects on dimensionless temperature profile for no viscous heating case with symmetrically heating (a) microannulus with β=0.5 and (b) parallel plate microchannel

Grahic Jump Location
Figure 4

Distribution of dimensionless temperature at different values of η (a) microannulus with β=0.5 and (b) parallel plate microchannel

Grahic Jump Location
Figure 3

Distribution of dimensionless temperature at different values of Brinkman number for parallel plate microchannel (a) η=0 and (b) η=1

Grahic Jump Location
Figure 2

Distribution of dimensionless temperature at different values of Brinkman number for microannulus with β=0.5 (a) η=0 and (b) η=1

Tables

Errata

Discussions

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