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. 2014 Jan 13;9(1):15.
doi: 10.1186/1556-276X-9-15.

Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets

Mohammad Mehrali, Emad Sadeghinezhad  1 , Sara Tahan Latibari, Salim Newaz Kazi, Mehdi Mehrali, Mohd Nashrul Bin Mohd Zubir, Hendrik Simon Cornelis Metselaar
Affiliations

Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets

Mohammad Mehrali et al. Nanoscale Res Lett. .

Abstract

In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m2/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m2/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems.

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Figures

Figure 1
Figure 1
Photo of GNP nanofluids after 600 h of storage time.
Figure 2
Figure 2
TEM images of GNP nanoparticles. (A) GNP 300, (B) GNP 500, and (C) GNP 750.
Figure 3
Figure 3
UV–vis spectrophotometers of GNPs nanofluids. (A, B, C) UV–vis spectrophotometer of GNPs nanofluids at different concentrations and wavelength and (D, E, F) absorption values of GNPs dispersed in distilled water at different concentrations.
Figure 4
Figure 4
Relative particle concentration of nanofluids with sediment time.
Figure 5
Figure 5
Zeta potential values of GNP (750 m 2 /g) nanofluids as a function of pH value.
Figure 6
Figure 6
Viscosity versus concentration at various temperatures and constant shear rates.
Figure 7
Figure 7
Plots of viscosity versus shear rate at various concentrations and temperatures.
Figure 8
Figure 8
Comparison between distilled water data from KD2pro and previous data.
Figure 9
Figure 9
Thermal conductivity of GNP nanofluids by changing of temperature with different GNP concentrations. (A) 0.025 wt.%, (B) 0.05 wt.%, (C) 0.075 wt.%, and (D) 0.1 wt.%.
Figure 10
Figure 10
Thermal conductivity ratios of GNPs with different concentrations and specific surface areas. (A) GNP 300, (B) GNP 500, and (C) GNP 750.
Figure 11
Figure 11
Thermal conductivity enhancement based on Nan's model and experimental results at 30°C.
Figure 12
Figure 12
Electrical conductivity ( σ ) of GNPs.
See this image and copyright information in PMC

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