Abstract

A new CFD modeling approach is developed and applied to a numerical study of pool boiling. It is based on a coupled simultaneous solving of the two-fluid model of two-phase flow in the boiling pool and the transient heat conduction within the heated wall. The applied two-fluid model consist in mass, momentum and energy balance equations for each phase and the closure laws for interface transport due to friction and phase transition. The boiling two-fluid mixture is thermally coupled with the heated wall by the heat transfer at the bubble footprint at randomly determined discrete locations of the nucleation sites and by the conjugate heat transfer from the heated wall to the wetting liquid on the surface outside the nucleation sites. The model is validated against detailed experimental data from the literature. Sensitivity analysis is performed to evaluate the influence of pool boiling parameters and conditions on the boiling curve, such as the nucleation site density, the wetting contact angle, the wall thermal conductivity, the wall thickness, the wall volumetric or bottom surface heating and the liquid volume in the pool. Temperature transients at the bubble nucleation sites are evaluated. The two-phase mixture pattern in pool boiling and the related swell level position can be well predicted with the nonuniform heat flux determined by the discrete nucleation sites of bubble growth and conjugate heat transfer from the heated wall to wetting liquid. The developed computational method is efficient and robust, while the reliability of its prediction is sensitive to the accuracy of nucleation site density and contact angle input data, as parameters that describe the coupled thermal and physical characteristics at the fluid-wall interface.

摘要

开发了一种新的 CFD 建模方法并将其应用于池沸腾的数值研究。它基于对沸腾池中两相流和受热壁内瞬态热传导的双流体模型的耦​​合同时求解。应用的双流体模型包括每个相的质量、动量和能量平衡方程以及由于摩擦和相变引起的界面传输的闭合定律。沸腾的二流体混合物通过在随机确定的成核位置的离散位置处的气泡足迹处的传热以及从加热壁到成核外表面上的润湿液体的共轭传热与加热壁热耦合网站。该模型根据文献中的详细实验数据进行了验证。进行敏感性分析以评估池沸腾参数和条件对沸腾曲线的影响，例如成核位点密度、润湿接触角、壁热导率、壁厚、壁体积或底面加热和液体池中的体积。评估气泡成核位置的温度瞬变。池沸腾中的两相混合物模式和相关的膨胀水平位置可以用由气泡生长的离散成核位置和从加热壁到润湿液体的共轭传热确定的非均匀热通量很好地预测。所开发的计算方法高效且稳健，而其预测的可靠性对成核位点密度和接触角输入数据的准确性很敏感，