• MEHDI MEHRABI

      Articles written in Bulletin of Materials Science

    • Experimental investigations into viscosity, pH and electrical conductivity of nanofluid prepared from palm kernel fibre and a mixture of water and ethylene glycol

      JUSTIN T AWUA JACOB S IBRAHIM SAHEED A ADIO MEHDI MEHRABI MOHSEN SHARIFPUR JOSUA P MEYER

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      Extensive research has been carried out on the synthesis and applications of nanofluid produced from metals, nonmetals and their oxides. However, little or no attention has been paid to bio-based nanoparticles. The need for the use ofbio-based nanoparticles and bio-based nanofluids is imperative to mitigate over-dependence on toxic synthetic nanoparticles. This idea is also in line with renewable and sustainable developmental goals.Moreover, bio-based materials like palm kernel fibre (PKF) constitute environmental waste in some quarters and its conversion to useful products for engineering application will take a long time in solving environmental issues and health hazards. In this study, the top-down approach was used to synthesize nanoparticles from PKF using a ball-milling machine. The PKF nanoparticles with an average size of $\sim$40 nmwere dispersed in an ethylene glycol (EG)/water (50:50) base fluid up to 0.5% of the volume fraction. The viscosity, pH and electrical conductivity of PKF–water and EG (50:50) were studied for temperature ranging from 10 to 60$^{\circ}$C. The results showed that the viscosity of the PKF-based nanofluid increases with an increase in volume fraction and decreases exponentially with an increase in the working temperature of the nanofluid. The pH and the electrical conductivity increased as the volume fraction of the PKF nanoparticle was increased from 0.1 to 0.5%. However, the pH decreased with an increase in the temperature while the electrical conductivity increased with an increase in the volume fraction. Since the notable theoretical models in the literature were unable to estimate the viscosity of the PKF–EG/water nanofluid, in the present case an empirical correlation based on dimensional analysis was proposed to estimate the viscosity of the PKF–EG/water nanofluids.

    • Electrical conductivity and pH modelling of magnesium oxide–ethylene glycol nanofluids

      MEHDI MEHRABI MOHSEN SHARIFPUR JOSUA P MEYER

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      Nanofluids as new composite fluids have found their place as one of the attractive research areas. In recent years, research has increased on using nanofluids as alternative heat transfer fluids to improve the efficiency of thermal systems without increasing their size. Therefore, the examination and approval of different novel modelling techniques on nanofluid properties have made progress in this area. Stability of the nanofluids is still an important concern. Research studies on nanofluids have indicated that electrical conductivity and pH are two important properties that have key roles in the stability of the nanofluid. In the present work, three different sizes of magnesium oxide (MgO) nanoparticles of 20, 40 and 100 nm at different volume fractions up to 3% of the base fluid of ethylene glycol (EG) were studied for pH and electrical conductivity modelling. The temperature of the nanofluids was between 20 and 70$^{\circ}$C for modelling. A genetic algorithm polynomial neural network hybrid system and an adaptive neuro-fuzzy inference system approach have been utilized to predict the pH and the electrical conductivity of MgO–EG nanofluids based on an experimental data set.

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