【摘要】 对含油制冷剂在6.34和2.50 mm换热管内的流动沸腾换热特性进行了实验研究,测试质量流率为200~400 kg/(m2.s),热流密度为3.2~14 kW/m2,蒸发温度为5°C,进口干度为0.1~0.8,干度变化0.1~0.2,平均油质量分数为0~0.05.定量分析了不同质量流率和干度时,润滑油对制冷剂在小管径换热管内流动沸腾换热的影响.与大管径换热管相比,油的换热增强效果在小管径换热管内减弱甚至消失,在高干度和高油浓度区,油的存在使换热严重恶化.对于上述换热管,换热系数、油影响因子以及基于制冷剂物性的两相换热增强因子随油浓度的变化规律缺乏一致性.采用局部油浓度下的制冷剂-润滑油混合物性计算得到的两相换热增强因子能较好地反映润滑油对制冷剂流动沸腾换热的影响.更多还原

【Abstract】 The flow boiling heat transfer performance inside small tubes with inside diameter of 6.34 mm and 2.50 mm was investigated with the test conditions of mass flux from 200 to 400 kg/(m~2·s),heat flux from 3.2 to 14 kW/m~2,evaporation temperature of 5(°C),inlet quality from 0.1 to 0.8,quality changing from 0.1 to 0.2 and nominal oil mass percent from 0 to 5.The oil enhanced effect shows weakened or diminished completely for small tube.The detrimental effect of oil in higher quality or oil concentration of small tube is much more significant than that of large tube and the heat transfer coefficient of mixture can be lower than 40% of pure refrigerant.The relationship between heat transfer coefficient,enhanced factor two phase multiplier with pure refrigerant properties and nominal oil mass fraction is unpronounced and inconsistent.The two phase multiplier with local refrigerant-oil mixture properties can reflect the oil influence on refrigerant heat transfer accurately and physically.更多还原