Model for predicting particle size evolution during nanoparticle aggregation in refrigerant-oil mixture

Nanorefrigerant-oil mixture is a promising energy-efficient refrigeration working fluid with superior thermophysical properties, and the prediction for its thermophysical properties requires the actual size of the particles in refrigerant-oil mixture. Due to the competitive adsorption of different liquid molecules on particle surface, the actual particle size of refrigerant-oil mixture cannot be predicted by the existing models developed for the nanofluids with single-component base fluid. This paper presents a model for predicting the particle size evolution during nanoparticle aggregation in refrigerant-oil mixture, considering the competitive adsorption behavior and its effects on particle movement and interaction. For model validation, the time-evolution of particle size distribution and the average size are calculated and compared with the existing experimental data. The model prediction agrees with 92% of the experimental data within deviation of ±10% and the mean deviation is 3.7%. In addition, the model can reflect the influences of oil mass fraction, initial particle concentration, primary nanoparticle diameter and temperature on particle size evolution. It is found that the adsorption layer has a significant effect on the aggregation behavior and the particle size evolution.