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Research Papers: Forced Convection

Temperature Rise in Electroosmotic Flow of Typical Non-Newtonian Biofluids Through Rectangular Microchannels

[+] Author and Article Information
Hadi Yavari

e-mail: hadiyavari@alum.sharif.edu

Arman Sadeghi

e-mail: armansadeghi@mech.sharif.edu

Mohammad Hassan Saidi

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

Suman Chakraborty

e-mail: suman@mech.iitkgp.ernet.in
Department of Mechanical Engineering,
Indian Institute of Technology,
Kharagpur 721302, India

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received March 27, 2013; final manuscript received September 16, 2013; published online November 21, 2013. Assoc. Editor: Giulio Lorenzini.

J. Heat Transfer 136(3), 031702 (Nov 21, 2013) (11 pages) Paper No: HT-13-1166; doi: 10.1115/1.4025561 History: Received March 27, 2013; Revised September 16, 2013

Electroosmosis is the main mechanism for flow generation in lab-on-a-chip (LOC) devices. The temperature rise due to the Joule heating phenomenon, associated with the electroosmosis, may be detrimental for samples being considered in LOCs. Hence, a complete understanding of the heat transfer physics associated with the electroosmotic flow is of high importance in design and active control of LOCs. The objective of the present study is to estimate the temperature rise and the thermal entry length in electroosmotic flow through rectangular microchannels, having potential applications in LOC devices. Along this line, the power-law rheological model is used to account for non-Newtonian behavior of the common biofluids encountered in these devices. A mixed type of thermal boundary condition is employed at the channel surface, instead of routinely presumed constant wall heat flux or constant wall temperature conditions. A finite difference-based numerical method is employed for solving the governing equations in dimensionless form. An approximate solution, based on the premise of a uniform temperature field throughout the channel cross section, is also obtained for the bulk mean temperature, which is found to be of high accuracy. This, accompanied by the assessments of the temperature profile, reveals that the temperature variations in the channel cross section are negligible, and as a result, the bulk mean temperature can be used as a very precise estimate of the maximum temperature in an LOC device. Moreover, the evaluation of the entry length shows that a thermally fully developed flow is hardly achieved in practical applications because of small length scales involved. Accordingly, the maximum temperature rise may significantly be smaller than what is calculated based on a thermally fully developed flow assumption.

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Figures

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Fig. 1

Schematic representation of the physical problem along with the coordinate system; EDLs are the regions between the dashed lines and the channel inner surface

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Fig. 2

Comparison between the bulk mean temperature values obtained in the present study and those reported by Iverson et al. [46]

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Fig. 3

Dimensionless bulk mean temperature values obtained by means of the numerical and approximate solutions versus the dimensionless axial position

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Fig. 4

Dimensionless temperature distribution at two different axial positions: (a) z* = 15.8 and (b) z* = 986.4. Here, the flow parameters are the same as those of Fig. 3.

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Fig. 5

Dimensionless bulk mean temperature versus the dimensionless axial coordinate at different Biot numbers

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Fig. 6

Average thermal characteristics at different values of Bi drawn based on the similarity factors

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Fig. 7

Dimensionless bulk mean temperature versus the dimensionless axial position at different Peclet Numbers

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Fig. 8

Dimensionless bulk mean temperature versus the dimensionless axial position at different power law indices

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Fig. 9

Dimensionless bulk mean temperature versus the dimensionless axial position at different values of the dimensionless Debye–Hückel parameter

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Fig. 10

Dimensionless bulk mean temperature versus the dimensionless axial position at different values of the dimensionless zeta potential

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Fig. 11

Dimensionless bulk mean temperature versus the dimensionless axial position at different values of the channel aspect ratio

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