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Research Papers: Micro/Nanoscale Heat Transfer

Nanofluid Convection in Microtubes

[+] Author and Article Information
Joohyun Lee

Department of Mechanical Engineering, Stanford University, Stanford, CA 94305jhyunl@stanford.edu

Patricia E. Gharagozloo

Department of Mechanical Engineering, Stanford University, Stanford, CA 94305perahm@stanford.edu

Babajide Kolade, John K. Eaton, Kenneth E. Goodson

Department of Mechanical Engineering, Stanford University, Stanford, CA 94305

J. Heat Transfer 132(9), 092401 (Jul 07, 2010) (5 pages) doi:10.1115/1.4001637 History: Received December 12, 2009; Revised March 16, 2010; Published July 07, 2010; Online July 07, 2010

While there has been much previous research on the thermal conductivity and convection performance of nanofluids, these data are rarely reported together with effective viscosity data that govern the relevance for heat exchanger applications. We report here the effective convection coefficient and viscosity in microtubes (D=0.5mm) along with stationary thermal conductivity measurements for nanofluids based on spherical particles (Al2O3, ZnO, and CuO) and carbon nanotubes. Sample data include an effective convection coefficient increase of 5% for 3vol%Al2O3/DI water nanofluid, 13.3% for 4vol% CuO/DI water nanofluid, and 11.6% for 0.2vol% Carbon nanotube(CNT)/DI water nanofluid. When considered together with our viscosity measurement on the same fluids, we find that the only the CNT-based nanofluids are promising for microfluidic heat exchangers.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Scanning electron microscopy images of (a) Al2O3 nanoparticles(40–50 nm), (b) CuO nanoparticles(13–37 nm), (c) multiwall CNT(A) (10–30 nm and 1–10 μm), (d) multiwall CNT(B) (10–30 nm and 0.5–50 μm), and (e) multiwall CNT(C) (40–60 nm and 5–15 μm) after evaporation of deionized water in nanofluids

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Figure 2

Experimental apparatus of convection and pressure drop measurement. infrared camera measures the outside wall temperature of stainless steel tube heated by power supply; pressure transducer measures the pressure drop in the microtube

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Figure 3

Wall temperature distributions of DI water, 0.1 vol % and 0.2 vol % CNT(B)/DI water nanofluid data; effective thermal conductivity is extracted by performing conjugate simulation

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Figure 4

(a) Effective viscosity data of Al2O3/DI water, CuO/DI water, and ZnO/DI water nanofluids. Viscosity data were obtained by measuring the pressure drop in the microtube. Batchelor model of particle laden flow fail to predict the nanofluid viscosity. (b) Viscosity variation in CNT(B)/DI water nanofluids as a function of shear rate showing non-Newtonian shear-thinning behavior. Viscosity was measured using a rheometer.

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Figure 5

Schematic of experimental apparatus measuring thermal conductivity of stationary nanofluids

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Figure 6

Effective viscosity and heat transfer augmentation data of seven different nanofluids: CNT(A)/DI water, CNT(B)/DI water, CNT(C)/DI water, CuO/DI water, Al2O3/DI water, ZnO/DI water, and premade Al2O3/DI water; all data are obtained from microtube experiment

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Figure 7

Multiple parallel channels with each diameter of d; the total channel width is constant as C

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