Can the Temperature Dependence of the Heat Transfer Coefficient of the Wire–Nanofluid Interface Explain the “Anomalous” Thermal Conductivity of Nanofluids Measured by the Hot-Wire Method?
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It is suggested that a possible explanation for the “anomalous” thermal conductivity of nanofluids measured by the hot-wire method is the positive temperature dependence of the heat transfer coefficient of the hot-wire–nanofluid interface, which results from the positive temperature dependence of the energy exchanged during the particles’ collisions with the wire. It is shown qualitatively that this effect can result in an overestimate of the nanofluid’s thermal conductivity. It is concluded that the interpretation of the experimental data for the thermal conductivity of nanofluids, obtained by the hot-wire method, requires independently determined data for the heat transfer coefficients and their temperature dependence of the hot-wire nanofluid and the particle–fluid interfaces.
KeywordsInterfacial heat transfer coefficient Nanofluid Thermal conductivity Transient hot-wire method
The Department of Mechanical Engineering at the University of British Columbia, Vancouver, Canada, is gratefully acknowledged for providing me, as Visiting Professor, with the desk space and computer needed to conduct this study. I am indebted to Dr. J. R. Thomas, Jr., Professor Emeritus, Department of Mechanical Engineering, Virginia Polytechnic Institute, Blacksburg, Virginia, for deriving the equations required for determining the thermal conductance of the hot-wire–fluid interface. The editorial assistance provided by Mrs. K. Donaldson is much appreciated.
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