A semi-analytical model for the thermal conductivity of nanofluids and determination of the nanolayer thickness

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

44 Scopus Citations
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Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)202-214
Journal / PublicationInternational Journal of Heat and Mass Transfer
Volume70
Online published23 Nov 2013
Publication statusPublished - Mar 2014
Externally publishedYes

Abstract

Nanofluid shows a huge potential to be the next-generation heat transfer fluid since the nanoparticles can suspend in the base fluids for a long time and the thermal conductivity of the nanofluid can be far above those of convectional solid-liquid suspension. It has long been known that liquid molecules close to a solid surface can form a layer which is solid-like in structure, but little is known about the connection between this layer and the thermal properties of the suspension. In this study, a semi-analytical model for calculating the enhanced thermal conductivity of nanofluids is derived from the steady heat conduction equation in spherical coordinates. The effects of nanolayer thickness, nanoparticle size, volume fraction, thermal conductivity of nanoparticles and base fluid are discussed. A linear thermal conductivity profile inside the nanolayer is considered in the present model. The proposed model, while investigating the impact of the interfacial nanolayer on the effective thermal conductivity of nanofluids, provides an equation to determine its nanolayer thickness for different types of nanofluids. Hence, different relationships between the nanolayer thickness and the nanoparticle size are found for each type of nanofluid. Moreover, based on the present model's prediction, it is found that the effective thermal conductivities of nanofluids show the same result as the Maxwell model when the nanolayer thickness value approaches to zero. Lastly, the effective thermal conductivities of different types of nanofluids calculated by the present model is in good agreement with the experimental results and the prediction is much better than the Maxwell model and Bruggeman model.

Research Area(s)

  • Effective thermal conductivity, Heat conduction, Mathematical model, Nanofluids, Nanolayer, Nanoparticles