基于非平衡热力学模型的管内沸腾过程模拟

Simulation of Boiling Flow in Vertical Tube Based on Non-Equilibrium Thermal Model

为了更准确地模拟壁面沸腾过程,根据Lavievile非平衡热力学模型对沸腾流动的壁面热流率进行了划分,通过调节函数结合Sato模型修正了沸腾流动中的混合k-ε模型,建立了同时适用于管内过冷沸腾与整体沸腾流动阶段的曳力模型。使用上述模型对环状竖直管内沸腾流动过程进行数值模拟,计算结果与实验值吻合,可以用来模拟整个管内沸腾流动过程。数值模拟显示,沸腾流动可以明显增大管壁的传热系数,但当管壁处蒸气体积分数超过0.6时,会出现传热恶化现象。

To simulate the boiling process,the wall heat flux was divided based on Lavievile's thermal non-equilibrium heat flux partition algorithm.The mixture k-ε turbulent model was improved by combination of Sato model and a modifier function,by which a new drag model was presented to simulate the full boiling flow in tube.The simulated result of boiling flow in vertical circular tube agreed with experiment data well,indicating that the model was valid in simulation of boiling flow in whole tube.It is found from the simulation that the wall heat transfer coefficient was evidently enhanced in boiling,however,heat transfer deterioration appeared when the volume fraction of vapor near the wall reached about 0.6.