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

(1)汽泡生长模拟程序的开发了一个数值模拟程序，分析了单个成核位置和两个相邻成核位置下汽泡的生长和合并。模拟结果表明了气泡作用下弯月形薄膜蒸发的重要性。(2)混合工质组成对流动沸腾的影响本文对R-134 a/R-124二元混合工质在水平管内进行了流动沸腾实验。混合物的组成对压降没有影响，而混合物的沸腾传热却显著降低。并对压降和传热的实测数据进行了关联。(3)混合物组成对三元混合物的影响研究在池核沸腾条件下，测定了三元混合制冷剂（R-134 a/R-142 b/R-123）的传热系数。传热系数的减少被认为是由于在液体-蒸汽界面处的更易挥发的组分的耗尽而导致的有效温差的减小。因此，沸程被认为是一个主导参数，并引入到一个关联式的沸腾传热系数的混合物。

(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.