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

(1)测量了不同双组分混合物和三组分混合物的核态沸腾换热系数。通过对测量数据的分析发现，与由混合物组分的换热系数估算的理想换热系数相比，换热系数的减小与沸腾范围有很大关系。因此，通过考虑沸腾范围作为一个关键参数，建立了传热关联式。建立的关联式在±25%的误差范围内成功地再现了双组分和三组分混合物的测量换热系数。(2)对7种双组分混合物的临界热流密度进行了测量。通过比较混合物各组分临界热流密度内插的理想临界热流密度，发现临界热流密度或增大或减小。正向混合工质提供了增加的临界热流密度，而负向混合工质提供了减小的临界热流密度。这种临界热流密度依赖于混合物性质的行为是在聚结气泡与加热壁之间的薄膜表面上形成Marangoni力的结果。为了实现这种混合物的临界热流机理，引入了无量纲Marangoni数，成功地建立了混合物沸腾临界热流密度的经验关联式。

(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.