Experimental Investigation on Preparation and Stability of Al2O3 Nanofluid In Deionized Water and Ethylene Glycol

Nanofluid has the potential as a cooling medium for the next generation fluid as it possesses many advantages in many engineering applications. However, one of the main challenges is to establish a well-dispersed nanoparticles system in a base fluid. The preparation technique of nanofluid plays an important part as it influences the measurement of thermal conductivity. Therefore, the objectives of this study are to evaluate the nanoparticle dispersion in different base fluid compositions and to determine the optimized suspension sonication time. In detail, 0.2 wt.% of Al2O3 nanofluid stability in the three ratios of base fluid (deionized water:ethylene glycol) 80:20, 70:30 and 60:40 were studied. The studies were based on a visual inspection and spectral absorbance analysis. It has clearly shown that the nanofluids prepared in 60:40 base fluid within 3 hours sonication time was the most stable suspension compared to other nanofluids. The visual inspection indicated nanofluid condition remains stable after 30 days. The spectral absorbance of nanofluids was recorded at 100 % for 5 days after preparation and remains above 95 % compared to the initial value, reflecting stable suspension. Hence the novelty of this work lies in the nanofluid stability based on sonication time and base fluid compositions.

The effect of nanoparticles on reservoir wettability alteration: a critical review

A novel concept of treating oil reservoirs by nanofluids is being developed to improve oil recovery and reduce the trapped oil in hydrocarbon reservoirs. Nanoparticles show great potential in enhancing oil recovery under ambient conditions. In this paper, the approaches of wettability alteration by using nanofluid, stability of nanofluids, and the most reliable wettability alteration mechanisms associated with variant types of nanoparticles have been reviewed. Moreover, the parameters that have a significant influence on nanofluid flooding have been discussed. Finally, the recent studies of the effect of nanoparticles on wettability alteration have been summarised and analysed. Furthermore, this paper presents possible opportunities and challenges regarding wettability alteration using nanofluids.

Stability and thermal conductivity of tri-hybrid nanofluids for high concentration in water-ethylene glycol (60:40)

Background: Research has been focused on improving the thermal properties of single nanofluid components for recent of years. Therefore, hybrid nanofluids or composites have been developed to improve heat transfer performance. Stability and thermal conductivity of the Al2O3-TiO2-SiO2 nanoparticles suspended in the fluid base of water (W) and ethylene glycol (EG) mixture with volume ratio of 60:40. Methods: Experiments were tri-hybrid nanofluid stability was investigated for volume concentration of 0.5 ~ 3.0%, and temperature conditions from 30 to 70 °C for thermal conductivity measurements using a KD2 Pro Thermal Properties Analyzer. The experimental results show that the tri-hybrid nanofluid stability analysis was performed using a stable UVVis method for up to 30 days after preparation with 10 hour sonication time. Results: Comparison of data concentration ratios with sedimentation for single, hybrid, and tri-hybrid nanofluids yielding a stable tri-hybrid nanofluid with 80-90% value. Evaluation of zeta potential for tri-hybrid nanofluids yielded 63.72 mV in excellent stability classification. Sedimentation of this visual observation is influenced by the gravity of the movement of particles in the tube after 30 days. Conclusion: The highest thermal conductivity for tri-hybrid nanofluids was obtained at 3.0% and a maximum increase of up to 27% higher than that of the basic fluid (EG/W). Tri-hybrid nanofluids with a concentration of 0.5% gave the lowest effective thermal conductivity of 13.4% at 70 °C.