RESEARCH ON PREDICTION METHODS OF HEAT TRANSFER COEFFICIENT AND CRITICAL HEAT FLUX IN BOILING OF MULTICOMPONENT MIXTURES

(1)测量了各种双组分和三组分混合物的有核沸腾传热系数。从实测数据分析中发现，传热系数相对于由混合物组分传热系数估算出的理想传热系数的减小与沸腾范围密切相关。因此，将沸腾范围作为一个关键参数，建立了传热关系式。建立的相关关系成功地再现了两组分和三组分混合物的测量传热系数，误差在±25%以内。(2)对7种双组分混合物进行了临界热流密度测量。将理想临界热流密度与混合组分的临界热流密度进行比较，发现临界热流密度不是增大就是减小。正混合能增加临界热流密度，而负混合能降低临界热流密度。这种临界热流密度随混合物性质的变化规律是由Marangoni力作用于凝聚气泡与加热壁之间形成的薄膜表面的结果。为了实现这种混合物的临界热流机制，引入了无因次Marangoni数，从而成功地建立了混合物沸腾临界热流的经验关系式。

(1)Heat transfer coefficients in nucleate boiling of mixtures were measured for various two-component mixtures and three-component mixtures. It was found from the measured data analysis that the reduction of heat transfer coefficient compared to the ideal coefficient estimated from heat transfer coefficient of mixture components is deeply related to the boiling range. Thus by taking into account the boiling range as a key parameter the heat transfer correlation was developed. The developed correlation succeeded to reproduce the measured heat transfer coefficients of two-and three-component mixtures within ±25% errors.(2)Measurement of critical heat flux was performed for seven two-component mixtures. It was found that critical heat flux is either increased or decreased in 'a comparison of the ideal critical heat flux interpolated between the critical heat fluxes of mixture components. Positive mixtures provided the increased critical heat flux, while negative mixtures gave the decreased critical heat flux. Such a behavior of critical heat flux depending on the mixture property was concluded as the result of Marangoni force acting on thin film surface formed between the coalesced bubble and the heating wall. In order to realize such critical heat flux mechanism of mixtures the dimensionless Marangoni number was introduced, resulting in successful development of an empirical correlation for critical heat flux in mixture boiling.