Thermophysical properties of methanol based nanofluids / Mohd. Mostafizur Rahman

Mohd. Mostafizur, Rahman (2015) Thermophysical properties of methanol based nanofluids / Mohd. Mostafizur Rahman. Masters thesis, University of Malaya.

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Abstract

Nanofluids are defined as colloidal suspension of solid particles with the size smaller than 100 nanometer. In this study, Al2O3, SiO2 and TiO2 nanoparticles were suspended into methanol without any surfactant to investigate their characteristics, stability and thermophysical properties. Nanoparticles size, shape, elemental proportion and suspension uniformity were characterized. The stability of methanol based nanofluids was analyzed using Uv-Vis spectrometer and zeta potential. Thermophysical properties of nanofluids, namely thermal conductivity, viscosity and density of nanofluids were measured by KD2 pro analyzer, LVDV III ultra–programmable rheometer and KEM-DA 130N density meter, respectively. All experiments were conducted at five different volume concentrations (0.005, 0.01, 0.05, 0.10 and 0.15 vol%) and five different temperatures (1, 5, 10, 15 and 20 ºC). In this study, Al2O3-methanol nanofluid appeared to be more stable compared to SiO2-methanol and TiO2-methanol nanofluids. It was found that thermal conductivity increased with the increase of volume concentration of nanoparticles for all types of nanoparticles. Thermal conductivity enhancements is shown between 1–8% for every 0.05 vol% increase with Al2O3 having the highest enhancement increase in nanoparticle volume concentration. Thermal conductivity also increased between 0.5–3.9% for every 5 °C increment in temperature with SiO2 showing the least change. The shear stress and viscosity increased with volume concentration but decreased with increase in temperature and shear rate. The results showed that the fluids appeared as a non-Newtonian fluid with a shear thickening or dilatant behavior. The increment was higher in TiO2–methanol nanofluids compared to the other two with the highest increment of 17.8%. Besides, density of the methanol based nanofluids increased with volume concentrations. However, density decreased accordingly with increased temperature. This study demonstrates that thermal conductivity, viscosity and density of methanol based nanofluids depend on the volume concentration and temperature.

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