目前还没有一种被广泛承认的理论能够解释高压过冷池沸腾换热,其机理尚不明确。为了揭示高压池内过冷核沸腾的物理传热机理,并获得气泡脱离频率与活化穴半径的函数关系,根据池内过冷核沸腾加热表面活化穴的分布,在统计方法的基础上,提出了高压池内过冷核沸腾的一个数学模型。从该模型中发现,池内过冷核沸腾热流密度是壁面过热度、液体过冷度、活化穴尺寸、流体的接触角以及流体物理特性的函数。对不同的过冷度,将模型预测的结果与实验数据进行了比较,两者吻合得极好,从而证明了数学模型的可靠性。该解析模型更深刻地揭示了过冷池沸腾换热的物理机理,且没有增加新的经验常数。
There is not a widely recognized theory which can explain the heat transfer of subcooled pool boiling under high pressure, so the mechanism of heat transfer of subcooled pool boiling is not clear. In order to disclosure the physical mechanisms of heat transfer for the subcooled nucleate pool boiling and obtain the relation between the bubble departure frequency and active cavity radius, the functions of heat transfer were analyzed according to the distribution of active cavity on boiling surfaces. A mathematical model was derived based on statistical treatment for the subcooled nucleate pool boiling heat transfer under high pressure. The proposed model for the heat flux of the subcooled nucleate pool boiling heat transfer is found to be a function of wall superheat, liquid subcooling, active cavity size, the contact angle and physical properties of fluid. No additional or new empirical constant is introduced. Comparing the model predictions with the existing experimental data, an excellent agreement between the model predictions and experimental data is found for different liquid subcoolings. The validity of the mathematical model for the subcooled nucleate pool boiling is thus verified. The analytical model reveals the physical principles of the heat transfer of subcooled pool boiling.