Influence of different parameters and their coupled effects on the stability of alumina nanofluids by a fractional factorial design approach

Abstract Nanofluids have been introduced as new-generation fluids able to improve energy efficiency in heat exchangers. However, stability problems related to both agglomeration and sedimentation of nanoparticles have limited industrial-level scaling. A fractional factorial experimental 2 k−1 design was applied in order to evaluate the effects of nanoparticle concentration, surfactant type and concentration, ultrasonic amplitude as well as ultrasonic time on the stability of alumina (Al 2 O 3 ) nanofluids. Commercial alumina nanoparticles (particle diameter 2 O 3 , CTAB, critical micelle surfactant concentration, 30% ultrasonic amplitude and 30 min of ultrasonication.