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Forced Convection

Effect of Flow Pulsation on the Heat Transfer Performance of a Minichannel Heat Sink

[+] Author and Article Information
Tim Persoons1 n2

School of Mechanical Engineering,  Purdue University, 585 Purdue Mall, West Lafayette, IN 47907timpersoons@purdue.edu

Tom Saenen, Tijs Van Oevelen, Martine Baelmans

Department of Mechanical Engineering,  Katholieke Universiteit Leuven, Celestijnenlaan 300A, 3001 Leuven, Belgium

1

Corresponding author.

2

Current address: Department of Mechanical and Manufacturing Engineering, Trinity College, University of Dublin, Parsons Building, Dublin 2, Ireland.

J. Heat Transfer 134(9), 091702 (Jul 09, 2012) (7 pages) doi:10.1115/1.4006485 History: Received March 25, 2011; Revised March 21, 2012; Published July 09, 2012; Online July 09, 2012

Heat sinks with liquid forced convection in microchannels are targeted for cooling electronic devices with a high dissipated power density. Given the inherent stability problems associated with two-phase microchannel heat transfer, this paper investigates experimentally the potential for enhancing single-phase convection cooling rates by applying pulsating flow. To this end, a pulsator device is developed which allows independent continuous control of pulsation amplitude and frequency. For a single minichannel geometry (1.9 mm hydraulic diameter) and a wide range of parameters (steady and pulsating Reynolds number, Womersley number), experimental results are presented for the overall heat transfer enhancement compared to the steady flow case. Enhancement factors up to 40% are observed for the investigated parameter range (Reynolds number between 100 and 650, ratio of pulsating to steady Reynolds number between 0.002 and 3, Womersley number between 6 and 17). Two regimes can be discerned: for low pulsation amplitude (corresponding to a ratio of pulsating to steady Reynolds number below 0.2), a small heat transfer reduction is observed similar to earlier analytical and numerical predictions. For higher amplitudes, a significant heat transfer enhancement is observed with a good correspondence to a power law correlation. This work establishes a reference case for future studies of the effect of flow unsteadiness in small scale heat sinks.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Instrumented minichannel heat sink and heater unit: (1) aluminum cover plate with fluidic connections, (2) aluminum channel plate (H = 1 mm, W = 16 mm, L = 32 mm, hydraulic diameter = 1.9 mm), and (3) insulated heater block

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Figure 2

Minichannel heat sink test facility with inline pulsating flow device

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Figure 3

Pulsator device for generating pulsating flow component with adjustable amplitude and frequency: (a) manifolds with check valves, (b) two pumping chambers operating in opposite phase, and (c) piezoelectric bending disk actuator

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Figure 4

Average Nusselt number for steady flow through the heat sink compared to established correlations for developing flow between parallel plates (W = ∞) [24-25] and a rectangular channel (W = 10H) [26]. Circular markers represent the experimental data for this heat sink (W = 16H), fitted by the correlation in Eq. 2.

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Figure 5

Dimensionless heat transfer enhancement δNu (see Eq. 3) as percentage (δNu × 100%) for pulsating flow through the heat sink as a function of the steady flow Reynolds number Re. Markers represent different pulsating Reynolds numbers Rep .

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Figure 6

Dimensionless heat transfer enhancement δNu (see Eq. 3) as percentage (δNu × 100%) for pulsating flow through the heat sink as a function of the ratio of pulsating to steady velocity component Rep /Re: (a) linear and (b) nonlinear axis scales. Open markers represent experiments at different frequencies 5≤f≤40Hz(6≤Wo≤17). Cross markers represent the numerical results of Craciunescu and Clegg [10]. The solid line represents the correlation in Eq. 4.

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Figure 7

Dimensionless heat transfer enhancement δNu as percentage (δNu × 100%) showing the same data as Fig. 6. Open markers represent experiments at different frequencies 5≤f≤40Hz(6≤Wo≤17). The solid line represents the correlation in Eq. 4. The two dashed lines represent the theoretical model expression in Eq. 7 evaluated for f = 5 Hz and f = 40 Hz.

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