THE MIXTURE HETEROGENEOUS BUBBLE NUCLEATION MODEL BASED ON THERMODYNAMIC PROPERTIES OF NONIDEAL FLUIDS

The formation of heterogeneous bubbles on the surface of the mixture has significant effects on the boiling heat transfer process. Based on thermodynamic properties of nonideal fluids and changes in Gibbs free energy between vapor and liquid ΔG, the heterogeneous nucleation model of the mixture is developed in this study. The Peng–Robinson equation of state and the van der Waals mixing rule are applied to obtain the metastable state thermodynamic properties of mixtures during heterogeneous nucleation. The critical radius, the quantity ΔG, the onset of nucleate boiling (ONB) superheat, and heat flux can be obtained from the model. The critical radius and ONB superheat increase at first, then decrease with an increase in the mole fraction of the volatile component. In comparison with the nucleation model based on ideal fluids, the proposed model based on real fluids presents a larger critical radius and ΔG during nucleation. Due to the higher energy barrier, a huger ONB superheat is required for the real fluids than ideal fluids for the same heat flux. Based on the thermodynamic properties of nonideal fluids, the improved heterogeneous nucleation model is consistent with experimental data. The mean absolute relative deviations are 22.72% for R124/R22 mixture and 27.85% for R134a/R245fa mixture compared with experimental data, which is better than that based on ideal mixtures of 30.09% for R124/R22 mixtures and 32.96% for R134a/R245fa mixtures.