Effects of sequence preparation of titanium dioxide-water nanofluid using cetyltrimethylammonium bromide surfactant and Tio₂ nanoparticles for enhancement of thermal conductivity

To maintain the stability of nanofluid from precipitation and agglomeration, some methods such as ultrasonic vibration, adding surfactant, and controlling the pH value of the system have been studied. Herein, the preparation of titanium dioxide (TiO₂)-water nanofluid, by using TiO₂ nanoparticles (TiO₂ NPs) and the cationic surfactant cetyltrimethylammonium bromide (CTAB), was investigated to determine the effects of the sequence method on the preparation of TiO₂-water nanofluid, its thermal conductivity, its stability, and its temperature distribution. NPs can improve the efficiency of heat transfer fluids and improving the stability of colloidal systems. Some parameters were varied, including sonication times of 5, 10, and 30 minutes, variations of TiO₂ loading in 1-8% volumetric loading, concentrations of CTAB (0.005-0.035 wt%), and pH at 8-12. The procedure sequences of 2 and 5 showed the distribution particle size of TiO₂ nanoparticles in nanofluid had a narrow range (190.3-208.7 nm) compared to other sequence methods (611 nm-5.35 μm). The procedure sequence of 2 is following demineralized water (100 mL), 8% volumetric loading of TiO₂ NPs, ultrasonication time of 10 min and CTAB of 3.2×10^-3 M, while the procedure sequence of 5 is in the respective order of demineralized water (100 mL), 8% volumetric loading of TiO₂ NPs, ultrasonication time of 10 min and pH at 8. The CTAB surfactant (0.029 wt%) had a greater influence on particle distribution in the nanofluid than the pH. The thermal conductivities of the nanofluid were characterized with TiO₂ nanofluid as the working fluid. The experimental results showed a maximum of 21% thermal conductivity enhancement for 8% volumetric loading of TiO₂ NPs at pH 8 and fourfold increase in critical micelle concentration (0.029 wt%) from CTAB. These findings offer the potential for preparing a stable TiO₂-water nanofluid with a short ultrasonic time of 10 minutes. This process is a desirable and very useful to obtain a stable TiO₂-water nanofluid with a short ultrasonic time for efficient process and low-cost nanofluid with high thermal conductivity and stability.