Preparation and stability of Al2O3 nano-particle suspension of ammonia–water solution

Abstract In order to apply the techniques that nano-particles enhance the heat and mass transfer to the ammonia–water absorption refrigeration, 4 different types of mixtures of nano-particle and surfactant, by mixing α-Al2O3 with polyacrylic acid (PAA), α-Al2O3 with cetyl trimethyl ammonium bromide (CTAB), γ-Al2O3 with PAA and γ-Al2O3 with sodium dodecyl benzene sulfonate (SDBS) respectively, were added to the ammonia–water solution respectively to prepare 4 kinds of nanofluids. A series of experiments were performed to investigate the dispersion stability of each kind of nanofluid with different mass fractions of surfactant (PAA, CTAB and SDBS), different durations of supersonic vibration and different mass fractions of ammonia–water basefluid. The results show that the dispersion of Al2O3 nanofluids firstly increases to a maximum and then decreases with the increase of surfactant mass fraction. The dispersions of Al2O3 nanofluids are improved with the increase of the mass fraction of ammonia–water basefluid. The dispersions of three kinds of nanofluids containing the mixture of α-Al2O3 and PAA, γ-Al2O3 and PAA, as well as γ-Al2O3 and SDBS respectively are improved by appropriate period of supersonic vibration. However, the dispersion of the nanofluid containing α-Al2O3 and CTAB is deteriorated after the treatment of supersonic vibration. It is found that PAA is the optimal dispersant among the three kinds of surfactant used in the experiments. Both the nanofluid containing α-Al2O3 and the nanofluid containing γ-Al2O3 achieve the best dispersing performance when the mass mass fraction of PAA is 0.3% and the duration of supersonic vibration is 30 min.