Axisymmetric Numerical Investigation on Steam Bubble Condensation

Abstract

In order to obtain a high-accuracy and adaptable condensation phase change model, this paper selects the Nusselt number correlation formula that Kim proposed based on the experimental data and adjusts the Nusselt number in the bubble condensation process by calculating the phase change coefficient of the Lee model in the UDF. Through the simulation and fine-tuning of the 12 groups of operating conditions, the formula for the change of the phase change coefficient of the Lee model during the bubble condensation process is obtained. The accuracy and wide applicability of the variation formula are verified by comparison with various types of experimental data. The Lee model provides a certain reference for the numerical simulation of the bubble condensation process. The numerical simulation of the condensation process of vapor bubbles is carried out by using the formula of the phase change coefficient. The error between the simulation result of the bubble volume change and the experimental result is lower than ±15%, which basically verified the reliability of the numerical model adopted in this study. The bubble condensation process has been analyzed under various operating conditions. The simulation results show that when the bubble rises, disturbance occurs with the fluid and several tiny eddies are generated on the side of the bubble. Micro-circulation of the vapor inside the bubble accelerates the heat and mass transfer rate at the gas−liquid interface. When condensation occurs, the mass transfer rate at the interface is different and the pressure inside the bubble is higher than that around it.

Keywords

• bubble condensation
• modified lee model
• cfd
• multiphase flow