Maximizing Thermal Conductivity and Stability of Alumina and Titanium oxide Nanofluids Using Femtosecond Laser Irradiation

Abstract

Nanofluid has been considered as working fluid of future because of high thermal properties such as thermal conductivity, thermal diffusivity and heat transfer coefficient. Nanofluid manufactured by adding various nanoparticles such as metallic and nonmetallic nanoparticles to various base fluids has high surface area. So it has tendency to agglomerate and become lumpy. In this study, femtosecond laser irradiation technique is used to enhance thermal conductivity and stability by controlling cluster of suspension and modifying size of nanoparticles. Alumina (Al2O3) and titanium oxide (TiO2) nanoparticles with different mean diameters are used. The thermal conductivity is measured by 3 omega method widely used in measuring the thermal conductivity of thin film and liquid with small volume. And the commercial device which is Zetasizser nano ZS90 (Malvern instrument Inc., London, UK) is used to measure zeta-potential and Hydrodynamic diameter. The experimental result shows substantially enhancement of thermal conductivity and stability when laser is irradiated to nanofluid. The value of thermal conductivity increased as size of particles decreased and zeta-potential increased until the optimal condition by laser fluences and number of pulses. And the long-term stability still stayed in range of good stable condition for 30 days. And the XPS analysis was conducted to analyze the effect of laser irradiation on TiO2 nanofluid.