Study on the Analogy between Heat Transfer and Fluid Friction in Gas-Liquid Two-Phase Flow

(1)目的：研究蒸发管内两相流的换热特性。对于单相流，动量和换热之间的类比是很好的。为了预测蒸汽发生器内的换热系数，提出了两相流动量与换热的类比方法。通过对空气-水、蒸汽-水等两相系统的实验，验证了该类比的有效性。(2)方法：进行了以下三个实验项目。在实验数据的基础上进行了数值计算。1.同时测量了换热系数、压降和含气率。在此基础上，利用含气率将换热系数与摩擦压力损失的两相乘数进行了关联。在环空流区验证了该关联式的有效性。2.为了测量制冷剂蒸发流动的含气率，研制了多根光纤探头。测量了不同流型下截面含气率的分布。3.对汽水流动的对流沸腾换热特性进行了实验研究。在核沸腾被抑制的高质量区域，所提出的类比关系是有效的。4.采用单相流湍流模型对两相环状流进行了数值计算。气水两相流速度分布的实验结果与计算结果吻合较好。对于沸腾流动的换热系数，没有得到满意的结果。

(1) OBJECTIVE : This study is concerned with the heat transfer characteristics of two-phase flow in evaporating tubes. The analogy between momentum and heat transfer is well established for single-phase flow. To predict the heat transfer coefficient in steam generators, application of the analogy between momentum and heat transfer for two-phase flow was proposed. The Validity of the analogy was investigated by experiments for air-water, steam-water and other two-phase systems.(2)APPROACH : The following three experimental projects were conducted. Based on the experimental data, numerical calculation was carried out. 1. Heat transfer coefficient, pressure drop and void fraction were simultaneously measured. From the analogy the heat transfer coefficient was correlated with the two-phase multiplier of frictional pressure loss by using the void fraction. The validity of this correlation was clarified in annular flow region. 2. To measure void fraction of evaporating flow of refrigerant, multiple optical fiber probe was developed. Profiles of void fraction in a cross section were measured for various flow regime. 3. Convective boiling heat transfer characteristics were investigated by experiment for steam-water flow. In high quality region where nucleate boiling was suppressed, proposed relationship of the analogy was valid. 4. Numerical calculation was carried out for two-phase annular flow by using a turbulence model for single-phase flow. Agreement between experiments and calculation was fairly well for velocity profiles of air-water flow. As for the heat transfer coefficient of boiling flow satisfactory results were not obtained.