International Journal of Technology 10(7): 1453-1464 ISSN 2086-9614 © IJTech 2019 EFFECTS OF SEQUENCE PREPARATION OF TITANIUM DIOXIDE–WATER NANOFLUID USING CETYLTRIMETHYLAMMONIUM BROMIDE SURFACTANT AND TiO2 NANOPARTICLES FOR ENHANCEMENT OF THERMAL CONDUCTIVITY Eny Kusrini 1* , Nandy Putra 2 , Agung Siswahyu 1 , Dewi Tristatini 1 , Wuwuh Wijang Prihandini 1 , Muhammad Idrus Alhamid 3 , Yoki Yulizar 4 , Anwar Usman 5 1 Department of Chemical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus Baru UI, Depok 16424, Indonesia 2 Applied Heat Transfer Research Group, Department of Mechanical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus Baru UI, Depok 16424, Indonesia 3 Department of Mechanical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus Baru UI, Depok 16424, Indonesia 4 Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Kampus Baru UI, Depok 16424, Indonesia 5 Department of Chemistry, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE1410, Brunei Darussalam (Received: August 2019 / Revised: October 2019 / Accepted: November 2019) ABSTRACT 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 m). 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 * Corresponding author’s email : ekusrini@che.ui.ac.id, Tel. +62-21-7863516 ext. 204, Fax: +62-21-7863515 Permalink/DOI: https://dx.doi.org/10.14716/ijtech.v10i7.3758