Synthesis and characterization of γ-Al2O3-Water nanofluid with and without surfactant

Abstract

Nanofluid is an attractive option to be used as a working fluid in various heat transfer applications due to its higher thermal conductivity and heat transfer coefficient compared to a conventional working fluid. One of the major obstacles using nanofluids is their long-term stability. This research aims to synthesize stable nanofluid to evaluate thermophysical properties of nanofluids such as thermal conductivity and viscosity. It also covers the effect of surfactant on stability and thermophysical properties of nanofluids. γ-Al2O3 having 99.9% purity and 20 nm average particle size is used as nanoparticle and deionized water is used as base fluid to synthesize stable nanofluid. Nanoparticles are synthesized in base fluid with various volume fractions of 0.3, 0.5, and 0.75% by two-step method. Effect of SDBS surfactant on stability and thermophysical properties are investigated in current research. Stability of nanofluid is investigated using various techniques such as Visual inspection, DLS, and UV–vis spectrometry. KD2Pro Thermal Analyzer and Anton Paar Rheometer are employed to evaluate thermal conductivity and viscosity of nanofluid. Experimental results depict insignificant improvement in stability of nanofluid with the use of surfactant. Results also show an increase in thermal conductivity and viscosity with rise in volume fraction. Maximum augmentation in thermal conductivity and viscosity is found as 8% and 20% for 0.75% volume fraction nanofluids synthesized without surfactant compared to base fluid. Use of surfactant shows an average drop in thermal conductivity by 3% and an average rise in viscosity by 2% for all volume fractions. Due to overall adverse impact of surfactant, its use is inadvisable in synthesis of nanofluid up to 0.75% volume fraction.