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Research Papers: Evaporation, Boiling, and Condensation

Investigation on Intertube Falling-Film Heat Transfer and Mode Transitions of Aqueous-Alumina Nanofluids

[+] Author and Article Information
Binglu Ruan1

School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, PR of China; Mechanical Science and Engineering, University of Illinois, Urbana, IL 61801bingluruan@gmail.com

Anthony M. Jacobi

Mechanical Science and Engineering, University of Illinois, Urbana, IL 61801a-jacobi@illinois.edu

1

Corresponding author.

J. Heat Transfer 133(5), 051501 (Jan 31, 2011) (11 pages) doi:10.1115/1.4002980 History: Received October 02, 2009; Revised June 22, 2010; Published January 31, 2011; Online January 31, 2011

Horizontal-tube falling-film heat transfer characteristics of aqueous aluminum oxide nanofluids at concentrations of 0vol%, 0.05vol%(0.20wt%), 0.5vol%(1.96wt%), 1vol%(3.86wt%) (with and without sodium dodecylbenzene sulfonate), and 2vol%(7.51wt%) are investigated and compared with predictions developed for conventional fluids. The thermophysical properties of the nanofluids, including thermal conductivity, kinematic viscosity, and surface tension, are reported, as is the mode transition behavior of the nanofluids. The experimental results for heat transfer are in good agreement with predictions for falling-film flow and no unusual Nu enhancement was observed in the present studies. Additionally, a 20% mode transitional Reynolds number increase was recorded for transitions between sheets and jets and jet-droplet mode to droplet mode. Although the findings with water-alumina nanofluids are not encouraging with respect to heat transfer, the results extend nanofluid data to a new type of flow and may help improve our understanding of nanofluid behavior. Moreover, this work provides a basis for further work on falling-film nanofluids.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of the experimental apparatus

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Figure 2

Falling-film liquid distributor

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Figure 3

Thermocouple placement on the test specimen tube

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Figure 4

TEM images of dispersed aluminum oxide nanofluid: (a) 0.5% and (b) 2%

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Figure 5

Measured thermal conductivity ratio of alumina nanofluids at different concentrations and the comparison between experimental data and literature

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Figure 6

Measured kinematic viscosity of nanofluids: (a) behavior with temperature at different concentrations and (b) behavior with nanofluid volume concentration at 30°C (curve shown for readability)

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Figure 7

Measured surface tension at different nanofluid concentrations

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Figure 8

Falling-film, heat transfer for pure water: (a) Nusselt number behavior with Re compared with prediction per Hu and Jacobi (3), (b) Nu comparison between experimental data and prediction per Hu and Jacobi (3) for three falling-film modes, and (c) comparison of heat transfer coefficients from the present experiments in droplet mode by Ganic and Roppo (18)

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Figure 9

Nusselt number comparison between experimental data for nanofluids and prediction per Hu and Jacobi (3) for the (a) sheet mode, (b) enlarged region of interest

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Figure 10

Nusselt number comparison between experimental data for nanofluids and prediction per Hu and Jacobi (3) for (a) jet mode, (b) enlarged region of interest

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Figure 11

Nusselt number comparison between experimental data for nanofluids and prediction per Hu and Jacobi (3) for droplet mode

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Figure 12

Nusselt number comparison between experimental data for nanofluids and prediction per Hu and Jacobi (3) for all falling-film modes

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Figure 13

Nusselt number comparison between experimental data with 1 vol % nanofluid and prediction per Hu and Jacobi (3) for all falling-film modes with and without the surfactant SDBS

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Figure 14

Comparison of heat transfer coefficient ratio (nanofluids to water) behavior with fluid total mass flow rate per unit length Γ for sheet mode and jet mode

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Figure 15

Comparison of experimental transitional Re to prediction per Hu and Jacobi (20): (a) distilled water, (b) 0.05% nanofluid, (c) 0.5% nanofluid, (d) 1% nanofluid, and (e) 2% nanofluid

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