Influences of primary particle parameters and surfactant on aggregation behavior of nanoparticles in nanorefrigerant

• Time evolution of particle sizes in nanorefrigerant were experimentally investigated.
• Steady-state hydrodynamic diameter increases with the increase of primary particle size.
• Primary particle concentration has slight influence on steady-state particle size.
• Influence of surfactant concentration on steady-state particle size changes with surfactant type.

The aggregation behavior of nanoparticles is related to the stability and the heat transfer performance of nanorefrigerant during long-term operation. The objective of this study is to experimentally investigate the influences of primary particle parameters and surfactant on the aggregation of nanoparticles in nanorefrigerant. The refrigerant and nanoparticles used for the nanorefrigerant preparation were R141b and TiO2, respectively. The primary particle size included 25, 40, 60 and 100 nm. The primary particle concentration was from 25 to 500 mg L−1. Three surfactants including the anionic, cationic and nonionic surfactants were used in the experiments. The time evolution of particle sizes were measured by dynamic light scattering method. The experimental results indicate that the particle size can reach steady-state with the elapse of time. The steady-state hydrodynamic diameter increases by 127.6% with the increase of the primary particle size from 25 to 100 nm. The primary particle concentration has slight influence on the steady-state particle size. The influence of surfactant concentration on the steady-state particle size changes with the surfactant type.