Berger Bioucas FE, Damm C, Koller TM, Fröba AP (2025)
Publication Language: English
Publication Type: Journal article
Publication year: 2025
Book Volume: 46
Article Number: 132
Journal Issue: 9
DOI: 10.1007/s10765-025-03597-3
This work investigates the effect of the shape of oblate particles on the effective thermal conductivity λeff of nanofluids. Spherical silicon dioxide (SiO2) nanoparticles with a mean diameter of 176 nm were plastically deformed in a stirred media mill to obtain non-spherical oblate particles of nearly cylindrical shape without significantly changing the volume of the individual particles. This allowed to study 1-pentanol-based nanofluids with varying particle sphericity ψ of 1.00, 0.50, or 0.45 at particle volume fractions φp up to 0.16, which exceeds the value range by a factor of two compared to previous studies on nanofluids with non-spherical particles. Measurements of λeff and of the thermal conductivity of the base fluid 1-pentanol, λbf, were performed at temperatures T from (298.15 to 358.15) K at ambient pressure using a steady-state guarded parallel-plate instrument (GPPI) with an expanded (coverage factor k = 2) uncertainty between (2.0 and 2.2) %. The experimental results indicate that the varying shape of the particles with about ten times higher thermal conductivity than λbf does not have a significant effect on λeff within the experimental uncertainties over the investigated ranges of φp and T. This behavior is not reflected by the semi-empirical Hamilton-Crosser (HC) model that predicts an increase in the thermal conductivity ratio λeff·λbf−1 with decreasing ψ. A better representation is given by the correct formulation of the effective medium theory via the model of Nan et al., which can be applied to dispersions with completely misoriented ellipsoidal particles. This is apparently related to the counterbalance of the enhancing effect of non-spherical particles on λeff due to their orientation-averaged extended heat conduction paths along the heat flux compared to spherical particles and the reducing effect caused by a Kapitza resistance at the particle/liquid interface, which increases with decreasing ψ for a given φp.
APA:
Berger Bioucas, F.E., Damm, C., Koller, T.M., & Fröba, A.P. (2025). Effective Thermal Conductivity of 1-Pentanol-Based Nanofluids Containing Oblate Silicon Dioxide Nanoparticles. International Journal of Thermophysics, 46(9). https://doi.org/10.1007/s10765-025-03597-3
MLA:
Berger Bioucas, Francisco E., et al. "Effective Thermal Conductivity of 1-Pentanol-Based Nanofluids Containing Oblate Silicon Dioxide Nanoparticles." International Journal of Thermophysics 46.9 (2025).
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