Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets
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NANO EXPRESS
Open Access
Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets Mohammad Mehrali1, Emad Sadeghinezhad2*, Sara Tahan Latibari1, Salim Newaz Kazi1, Mehdi Mehrali1, Mohd Nashrul Bin Mohd Zubir2 and Hendrik Simon Cornelis Metselaar1
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. Keywords: Graphene nanoplatelets; Nanofluids; Thermal conductivity; Rheology; Stability
Background Processes of energy transport have been integrated in a wide range of areas, such as in industry, oil and gas, and electricity. In the past decades, ethylene glycol, water, and oil were used as conventional fluids in heat exchanger systems. However, improvement of these conventional heat transfer fluids, particularly thermal conductivity, has become more and more critical to the performance of energy systems [1]. Choi and Eastman [2] have introduced the term nanofluids referring to fluids containing dispersed nanosized particles having large thermal conductivity enhancement. In spite of the attention received by this field, uncertainties concerning the fundamental effects of nanoparticles on thermophysical properties of solvent media remain [3]. Thermal conductivity is the * Correspondence: [email protected] 2 Department of Mechanical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia Full list of author information is available at the end of the article
property that has catalyzed the attention of the nanofluid research community [4]. A lot of research has been devoted to improve the thermal properties of these fluids by adding a small quantity of a highly thermal conductive sol
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