Experimental Measurements on the Thermal Conductivity of Glycerol-Based Nanofluids with Different Thermal Contrasts

Mohamed Lotfi,Abderrahim Bakak,Abdellah Hadaoui,Abdelaziz Koumina,Rodolphe Heyd,Donglu Shi

doi:10.1155/2021/3190877

Abstract

We report, in this work, our study of the thermal conductivity of high-viscosity nanofluids based on glycerol. Three nanofluids have been prepared with different thermal contrasts, by suspending graphene flakes, copper oxides, or silica nanoparticles in pure glycerol. The nanofluids were thermally characterized at room temperature with the 3ω technique, with low amplitudes of the temperature oscillations. A significant enhancement of the thermal conductivity is found in both the glycerol/copper oxide and the glycerol/graphene flake nanofluids. Our results question the role played by the Brownian motion in the microscopic mechanisms of the thermal conductivity of high-viscosity glycerol-based nanofluids. A similar behavior of the thermal conductivity as a function of the nanoparticle volume fraction was found for all three glycerol-based nanofluids presently investigated. These results could be explained on the basis of fractal aggregation in the nanofluids.

Highlights

Over the last few years, the improvement of thermal transfer has become an imperative requirement for optimizing the use of energy in various industrial and technological fields, mainly due to the scarcity of fossil fuels exhorting the use of current resources more efficiently
It has been demonstrated that the dispersal of highly conductive nanoparticles in liquids, even in very small amounts, is able to increase the effective thermal conductivity of the base fluid by nearly 200% with carbon nanotubes (CNTs) for example [2] and by about 40% in the case of the copper oxide NPs [3]
With regard to the use of CNTs in heat dissipation, the heat transfer performance of CNT/water nanofluids (CNWNFs) was measured [5]; the measurements revealed that using CNTs at a concentration of 0.5 wt% in a horizontal tube enhanced heat transfer by 350%

Summary

Introduction

Over the last few years, the improvement of thermal transfer has become an imperative requirement for optimizing the use of energy in various industrial and technological fields, mainly due to the scarcity of fossil fuels exhorting the use of current resources more efficiently. According to the terminology introduced by Choi in 1995 [1], a nanofluid consists of a stable dispersion of nanoparticles (NPs) in a base liquid. This kind of dispersion has aroused considerable interest in the last few years since a significant improvement of the effective thermal conductivity has been achieved with several nanofluids. It has been demonstrated that the dispersal of highly conductive nanoparticles in liquids, even in very small amounts (less than 1% per volume), is able to increase the effective thermal conductivity of the base fluid by nearly 200% with carbon nanotubes (CNTs) for example [2] and by about 40% in the case of the copper oxide NPs [3]. With regard to the use of CNTs in heat dissipation, the heat transfer performance of CNT/water nanofluids (CNWNFs) was measured [5]; the measurements revealed that using CNTs at a concentration of 0.5 wt% in a horizontal tube enhanced heat transfer by 350%

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