INFLUENCE OF COMPOSITION ON HEAT TRANSFER AND CRITICAL HEAT FLUX IN BOILING OF MULTICOMPONENT MIXTURES

(1)气泡生长模拟程序的开发开发了一个数值模拟程序，用于分析单个成核点和相邻两个成核点的气泡生长和聚并过程。模拟结果明确了气泡作用下弯月面液膜蒸发的重要性。(2)流动沸腾中混合物组成的影响对二元混合工质(R-134a/R-124)在水平管内的流动沸腾实验进行了研究。混合工质的组成对压降影响不大，而混合工质的沸腾换热显著降低。实验测量了三元混合工质(R-134a/R-142b/R-123)在核态池沸腾中的换热系数。换热系数的降低可归因于有效温差的减小，这是由于液-汽界面上更易挥发的组分耗尽的结果。因此，将沸腾范围作为主要参数，并将其引入混合物的沸腾换热系数关联式。

(1) Development of Simulation Code for Bubble GrowthA numerical simulation code was developed to analyze the bubble growth and coalescence both for a single nucleation site and for two neighboring sites. Simulation results made clear an importance of evaporation from a meniscus film under bubbles.(2) Influence of Mixture Composition in Flow BoilingFlow boiling experiment was performed for binary refrigerant mixtures (R-134a/R-124) in a horizontal tube. Pressure drop was not influenced by mixture composition, while heat transfer was significantly reduced in mixture boiling. Measured data of pressure drop and heat transfer were correlated in empirical correlations.(3) Influence of Mixture Composition on Three Component MixturesHeat transfer coefficient of ternary refrigerant mixtures (R-134a/R-142b/R-123) was measured in nucleate pool boiling. Reduction in heat transfer coefficients was found attributable to a decrease of the effective temperature difference as a result of the depletion of the more volatile component at the liquid-Vapor interface. Thus the boiling range was considered as a dominant parameter and introduced in a correlation for boiling heat transfer coefficient of mixtures.