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Research Papers

Flow and Heat Transfer Analysis of an Electro-Osmotic Flow Micropump for Chip Cooling

[+] Author and Article Information
K. Pramod

Department of Mechanical Engineering,
Indian Institute of Technology Madras,
Chennai 600036, India

A. K. Sen

Department of Mechanical Engineering,
Indian Institute of Technology Madras,
Chennai 600036, India
e-mail: ashis@iitm.ac.in

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received December 23, 2013; final manuscript received May 9, 2014; published online June 5, 2014. Assoc. Editor: Pradip Dutta.

J. Electron. Packag 136(3), 031012 (Jun 05, 2014) (14 pages) Paper No: EP-13-1137; doi: 10.1115/1.4027657 History: Received December 23, 2013; Revised May 09, 2014

This paper reports theoretical and numerical analysis of fluid flow and heat transfer in a cascade electro-osmotic flow (EOF) micropump for chip cooling. A simple analytical model is developed to determine the temperature distribution in a two-dimensional (2D) single channel EOF micropump with forced convection due to a voltage difference between both ends. Numerical simulations are performed to determine the temperature distribution in the domain which is compared with that predicted by the model. A novel cascade EOF micropump with multiple microchannels in series and parallel and with an array of interdigitated electrodes along the flow direction is proposed. The simulations predict the maximum flow rate and pressure capability of one single stage of the micropump and the analytical model employs equivalent circuit theory to predict the total flow rate and back pressure. Each stage of the proposed micropump comprises sump and pump regions having opposing electric field directions. The various design parameters of the micropump includes the height of the pump and sump (h), number of stages (n), channel width (w), thickness of the channel wall or fin (r), and width ratio of the pump and sump (s:p) regions. Numerical simulations are performed to predict the effects of these design parameters on the pump performance which is compared with that predicted by the analytical model. The micropump is used for cooling cooling of an Intel® CoreTM i5 chip which produces a maximum heat of 95 W over an area of 3.75 × 3.75 cm. Based on the parametric studies a design for the cascade EOF micropump is proposed which provides a maximum flow rate of 14.16 ml/min and a maximum back pressure of 572.5 Pa to maintain a maximum chip temperature of 310.63 K.

Copyright © 2014 by ASME
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References

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Figures

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Fig. 1

Velocity profile v and the negative Debye layer charge density profile ρeq in an ideal EOF

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Fig. 2

EOF between two infinite parallel plates for forced convection

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Fig. 3

Energy conservation for an element of length dx

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Fig. 4

Expected temperature profile along x- and y-directions

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Fig. 5

Planar layout of the proposed 3D cascade EOF micropump

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Fig. 6

Schematic of a single stage of the cascade EOF micropump showing the design parameters

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Fig. 7

Section of a cascade EOF micropump with a single channel and single stage

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Fig. 8

The equivalent circuit model for calculating the total back pressure and flow rate

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Fig. 9

Variation of the temperature of bottom plate along x-direction

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Fig. 10

Variation of the temperature of fluid along y-direction (at x = 0.5 cm)

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Fig. 11

(a) Geometry of the heat transfer in EOF through parallel microchannels separated by channel walls (fins) and (b) surface plot of temperature plot across x–y plane

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Fig. 12

Variation of the temperature at the bottom wall along the flow direction at the center of the channel, i.e., y = 50 μm

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Fig. 13

Variation of the temperature along z-direction at the center of the channel, i.e., y = 50 μm and x = 0.5 cm

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Fig. 14

Surface plot of temperature on y–z plane

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Fig. 15

Variation of temperature in the y-direction at x = 0.5 cm and for different values of z

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Fig. 16

Conceptual model of a section of the 3D cascade EOF micropump used for simulation

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Fig. 17

Surface plot of (a) temperature on x–z plane and (b) temperature on y–z plane, x = 1500 mm

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Fig. 18

Pressure-flow (P-Q) characteristics of 3D cascade EOF micropump per stage per channel

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Fig. 19

Velocity profile in the sump and pump regions

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Fig. 20

(a) Variation of flow rate Q and back pressure ΔP and (b) temperature Tmax with number of stages n

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Fig. 21

(a) Variation of flow rate Q and back pressure ΔP and (b) temperature Tmax with sump-to-pump (s:p) width ratio

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Fig. 22

(a) Variation of flow rate Q and back pressure ΔP and (b) temperature Tmax with wall-to-channel (r:w) width ratio

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Fig. 23

(a) Variation of flow rate Q and back pressure ΔP and (b) temperature Tmax with channel aspect ratio (fixed h)

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Fig. 24

(a) Variation of flow rate Q and back pressure ΔP and (b) temperature Tmax with channel aspect ratio (fixed w)

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Fig. 25

Sketch of the top and bottom layers of the proposed device, the electrode patterns and access hole on the top layer, and the etched fluidic channels and posts/fins are shown

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Fig. 26

Schematic of the process flow for fabrication of the device

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