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Thermal properties and convective heat transfer of phase changing paraffin nanofluids

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journal contribution
posted on 06.07.2017 by Valtteri Mikkola, Salla Puupponen, Kari Saari, Tapio Ala-Nissila, Ari Seppala
Fluids containing micro-sized solid-liquid phase changing particles have been proposed to be promising candidates as future heat transfer fluids. In addition, smaller nano-sized particles have been claimed to enhance the heat transfer performance of fluids even if the phase change is not exploited. For the first time, we conduct full scale convection heat transfer measurements combining these two consepts. Three water-based paraffin mixture nanofluids with particle mass fractions of 5–10% are prepared and measured with an annular tube heat exchanger with Reynolds numbers varying in the range of 700–11000. In addition, the fluids are characterized: latent heats, specific heats, viscosities, thermal conductivities, densities and particle size distributions are all determined experimentally. In agreement with previous studies of solid-particle nanofluids and nanoemulsions, also the phase changing nanofluids are found to exhibit Nusselt numbers clearly higher (up to ∼60% in the turbulent regime) than water when compared on the basis of equal Reynolds numbers. However, the differences in Prandtl numbers are shown to explain these deviations in Nusselt numbers. Indeed, the well-known Gnielinski correlation is able to explain the results and thus, significant anomalies in the convection heat transfer caused by neither the melting of the phase change material nor the presence of the nanoparticles are observed. However, the nanofluids have systematically slightly higher Nusselt numbers than the correlation would predict, but the deviations are within the accuracy of the correlation (10%). When compared by using equal pumping powers, the nanofluids exhibit heat transfer performance poorer than that of water. The positive impact of the latent heat is outweighed by the negative effects of the increased viscosity and decreased specific heat.

Funding

The research was funded by the Aalto Energy Efficiency Research Programme (EXPECTS-project), Efficient Energy Use (EFEU) research program coordinated by CLEEN Ltd. with funding from the Finnish Funding Agency for Technology and Innovation, Tekes, and the Academy of Finland through its COMP CoE grants 251748 and 284621 (T. A-N.).

History

School

  • Science

Department

  • Mathematical Sciences

Published in

International Journal of Thermal Sciences

Volume

117

Pages

163 - 171

Citation

MIKKOLA, V. ... et al, 2017. Thermal properties and convective heat transfer of phase changing paraffin nanofluids. International Journal of Thermal Sciences, 117, pp. 163-171.

Publisher

© Elsevier Masson SAS

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

23/03/2017

Publication date

2017

Notes

This paper was published in the journal International Journal of Thermal Sciences and the definitive published version is available at http://dx.doi.org/10.1016/j.ijthermalsci.2017.03.024.

ISSN

1290-0729

Language

en

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