Experimental research on particle aggregation behavior in nanorefrigerant-oil mixture

The objective of this study is to experimentally investigate the effects of primary particle size, primary particle concentration and temperature on particle aggregation behavior in nanorefrigerant-oil mixture. The nanoparticles, refrigerant and lubricating oil for experiments were TiO2, R141b and ATMOS NM56, respectively. Experimental conditions included primary particle size from 25 to 100 nm, primary particle concentration from 50 to 500 mg L−1, temperature from 6 to 27 °C, and oil concentrations of 1, 3 and 5 wt%. Time evolutions of the hydrodynamic diameter of aggregates were measured by dynamic light scattering (DLS) method. It is shown that the presence of lubricating oil inhibits the particle aggregation, and the inhibition is strengthened with the increase of oil concentration; the hydrodynamic diameter of aggregates is enlarged with the increase of primary particle size, primary particle concentration or temperature, and the enlargement increases with the increase of oil concentration.