International Journal of Innovations in Engineering and Technology (IJIET) http://dx.doi.org/10.21172/ijiet.132.04 Volume 13 Issue 2 May 2019 026 ISSN: 2319-1058 An experimental study on the dispersion and stability of (CNT/Alumina) nanofluid Ajeong Lee 1 , Otgonbayar Dovjuu 2 , Yong Ho Park 3 , Hyomin Jeong 4 1,2,4 Dept. of Energy and Mech. Eng., Institute of Marine Industry, Gyeongsang National University, Cheondaegukchi-Gil 38, Tongyeong, 53064, South Korea 3 Department of Mechanical Eng., KOJE College, Majeon1-Gil, Geoje-si, South Korea Abstract- In recent years, nanofluids technology is proposed and studied due to their novel properties which make them potentially useful in many applications in heat transfer. Good dispersion of nanoparticles in the base fluid, which have been designated "nanofluid", exhibits enhanced thermal conductivity and higher heat transfer coefficient. The present study aimed to evaluate a simple, efficient approach to improve the dispersion of MWCNTs and Alumina particle aqueous media for preparing the hybrid nanofluid. Samples were prepared with a different mass ratio of CNT and Alumina nanoparticles (2:1; 1:1; 1:2) and two dispersion techniques were tested. Planetary Ball Milling performed for the CNT structure as a mechanical method to reduce the agglomerated size of particles and greatly enlarge the surface area of the CNT. Plus, cellulose material was used for the better solution. Dispersion quality of the hybrid nanofluids examined by UV-Vis spectroscopy. The experimental result showed the sample that was treated by mechanical and dispersant methods is the effective way for the dispersibility of the composite nanofluid along with stability. Keywords – Dispersion, Hybrid nanofluid, MWCNTs, Cellulose Nano Crystal, Planetary Ball Milling I. INTRODUCTION Nanofluids have been studied for the last decade with the huge potential to enhance the efficiency of the heat transfer characteristics [1-3]. Therefore, well-dispersed nanoparticles for nanofluids are very expected to improve mechanical performance through many industry [4-5]. Not surprisingly, CNTs dispersion homogeneity is indispensable for the further application of nanofluids. So, well-dispersed CNTs suspensions are one of most sought- after endeavors in the field of nanocomposite materials. To overcome dispersion issues, different approaches based on chemical and mechanical processes have been proposed and evaluated [6-7]. Some studies have been conducted on the improvement of dispersion. Munkhbayar et al. [8] reported a planetary ball milling method that are applied to enhance the dispersibility of nanoparticles in a base fluid distilled water. When CNC used as dispersion agent, CNT nanoparticle dispersed well in aqueous media. Due to the effect of the oppositely charged ions on the surface of the CNT and CNC, an interaction occurs which results in stable dispersion. [9] AciQinzhi Lia et al. [10] studied dispersion of nano-cellulose function of salinity and storage time. The cellulose nanocrystals (CNC) have become widespread in the many research [11-14]. It has rod-shaped nanoparticles obtained from the acid hydrolysis of cellulose. It is about from 10 to 100 nm in diameter and from 100 nm to 1000 nm in length, depending on the cellulose source and the hydrolysis conditions. CNC interact with water strongly through hydrogen bonding due to the hydroxyl groups on the cellulose molecule. In this study, the mechanical and chemical process were investigated to obtain well-dispersed hybrid nanofluids. II. EXPERIMENTAL DETAILS The MWCNTs and Alumina hybrid nanofluid were prepared with different ratio of CNT and Alumina (2:1; 1:1; 1:2) and two dispersion techniques were tested by Planetary Ball Milling and chemical and adding the dispersant for the nanofluid. MWCNTs nanoparticles were dispersed in aqueous using an ultrasonic bath (1510E- DTH Branson Ultrasonic Corporation, USA) for 2 hours. Wet grinding operations performed by planetary ball milling (HPM- 700, Haji Engineering, Korea) was used to shorten the length of the nanoparticles by the wet grinding process. In this study, Mono-sized (3.0 mm) spherical Zirconia (ZrO2) balls were used as the collision medium. The agitator -applied rotation speed was 500 rpm and the wet grinding process was 1 hour before the ultrasonication. The detailed process of this have been introduced in the previous research [8]. To make the better dispersion, CNC added to the ground MWCNTs as a dispersant. For both cases, samples were prepared with a different ratio of CNT and Alumina (2:1; 1:1; 1:2), the dispersion characteristic of CNT/Alumina hybrid nanofluid were examined with UV-Vis spectroscopy(xma 3100 spectrophotometer). III. EXPERIMENT AND RESULT Obtained results from UV/Vis measurement are presented in the Figures 1-4 which shows the dispersion characteristics and a variation of absorbance prepared nanofluids function as time.