Formation and growth of R32/R1234yf nanobubble on smooth surface: Molecular dynamics simulations

Abstract

The boiling process starts from the formation of bubbles on the heated surface and the bubble growth process determines the boiling heat transfer characteristics. It is of great significance to recognize the formation and growth mechanism of nanobubbles to improve the boiling heat transfer efficiency. R32/R1234yf has a great application potential in power system such as refrigeration and Organic Rankine Cycle. In this work, the bubble formation and growth process of pure and mixture working fluids on an ideal smooth heating surface were studied by MD. The influence of compositions on the bubble grow curve was analyzed with emphasis, the characteristics of local temperature and density distribution and bubble geometric parameters were also investigated. The results show that the addition of R1234yf in R32 can inhibit the nucleation and growth of bubbles. As the mole fraction of R1234yf increases, the inception time of bubble is delayed and the bubble grow rate decreases. In the inertia controlled stage, the bubble growth curves of R32/R1234yf mixtures are closer to those of R1234yf, the reason is that more R1234yf remains in the bubble during the rapid growth of bubble, resulting in the decrease of the mole fraction of R32 in the bubble near the interface. Based on the prediction model of bubble grow rate in liquid phase, a semi-theoretical model for predicting surface bubble grow rate is proposed by analogy, the average prediction deviation of the model is less than 10%.