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Research Papers: Micro/Nanoscale Heat Transfer

Design and Test of Carbon Nanotube Biwick Structure for High-Heat-Flux Phase Change Heat Transfer

[+] Author and Article Information
Qingjun Cai

 Teledyne Scientific & Imaging, 1049 Camino Dos Rios, Thousand Oaks, CA 91360qcai@teledyne.com

Chung-Lung Chen

 Teledyne Scientific & Imaging, 1049 Camino Dos Rios, Thousand Oaks, CA 91360

J. Heat Transfer 132(5), 052403 (Mar 09, 2010) (8 pages) doi:10.1115/1.4000469 History: Received June 19, 2009; Revised September 23, 2009; Published March 09, 2010; Online March 09, 2010

With the increase in power consumption in compact electronic devices, passive heat transfer cooling technologies with high-heat-flux characteristics are highly desired in microelectronic industries. Carbon nanotube (CNT) clusters have high thermal conductivity, nanopore size, and large porosity and can be used as wick structure in a heat pipe heatspreader to provide high capillary force for high-heat-flux thermal management. This paper reports investigations of high-heat-flux cooling of the CNT biwick structure, associated with the development of a reliable thermometer and high performance heater. The thermometer/heater is a 100-nm-thick and 600μm wide Z-shaped platinum wire resistor, fabricated on a thermally oxidized silicon substrate of a CNT sample to heat a 2×2mm2 wick area. As a heater, it provides a direct heating effect without a thermal interface and is capable of high-temperature operation over 800°C. As a thermometer, reliable temperature measurement is achieved by calibrating the resistance variation versus temperature after the annealing process is applied. The thermally oxidized layer on the silicon substrate is around 1-μm-thick and pinhole-free, which ensures the platinum thermometer/heater from the severe CNT growth environments without any electrical leakage. For high-heat-flux cooling, the CNT biwick structure is composed of 250μm tall and 100μm wide stripelike CNT clusters with 50μm stripe-spacers. Using 1×1cm2 CNT biwick samples, experiments are completed in both open and saturated environments. Experimental results demonstrate 600W/cm2 heat transfer capacity and good thermal and mass transport characteristics in the nanolevel porous media.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Platinum heater/thermometer on a glass die

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Figure 2

Calibration of resistance versus temperature of the platinum thermometer: (a) schematic diagram and (b) sample in calibration

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Figure 3

Resistance versus temperature before annealing

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Figure 4

Resistance versus temperature after annealing

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Figure 5

Test schematic for the maximum operating temperature of the platinum thermometer/heater

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Figure 6

Silicon substrate samples integrated with the platinum thermometer/heater

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Figure 7

Development of CNT biwick structure

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Figure 8

The R−T calibration result of the platinum thermometer/heater for high-heat-flux tests

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Figure 9

Test chamber for high-heat-flux experiments

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Figure 10

Resistance measurement circuit of the platinum thermometer/heater

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Figure 11

Modeling of heat spreader effect/heat loss in high-heat-flux tests

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Figure 12

Temperature measurement on sample electrode pad

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Figure 13

Intensive phase change on CNT biwick structure

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Figure 14

High-heat-flux experimental results in open environment

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Figure 15

High-heat-flux experimental results in saturated environment

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Figure 16

Comparison of heat transfer coefficient between microcopper and nano-CNT biwick structures

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Figure 17

Schematic diagram of the film evaporation for pillarlike wick structure

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Figure 18

Total thin-film evaporation area comparisons between nano- and micropillarlike wick structures

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