R290在水平微细圆管内沸腾换热特性研究

本文研究了R290在内径为1 mm、2 mm和4 mm水平微细圆管内的沸腾流动换热特性,在饱和温度为15℃条件下,质量流速为50～600 kg/(m~2·s)、干度为0～1、热流密度为5～20 k W/m~2时,对沸腾传热系数的影响进行了分析。通过实验发现,增大质量流速对传热系数具有增强作用,质量流速对传热系数的影响在低干度区域比高干度区域小。在热流密度方面,传热系数随着热流密度的增大而增大,且在1 mm和2 mm管内观察到了临界干度对传热系数的影响,这时传热系数有断崖式下降的趋势。在管径对于传热系数的影响方面,通过对不同管径换热特性的横向对比,发现在一定工况下传热系数随着管径的减小有所上升。此外本文还对R290已有的部分关联式进行了适配性验证。

Study on Boiling Heat Transfer Characteristics of R290 in Horizontal Micro-tubes

In this study the boiling heat transfer characteristics of R290 in a 1, 2, and 4 mm horizontal micro-tube were investigated experimentally. The effects of mass flow rate 50-600 kg/(m2?s)], quality (0-1), and heat flux (5-20 kW/m2) on the boiling heat transfer coefficient at a saturation temperature of 15 °C were analyzed. The results showed that increased mass flow velocity can enhance the heat transfer coefficient and the influence of mass flow rate on the heat transfer coefficient with low quality is smaller than that with high quality. The heat transfer coefficient increased with the increased heat flux, and the effect of critical quality on the heat transfer coefficient was apparent in 2 and 1 mm tubes. The heat transfer coefficient tended to decrease precipitously for 2 and 1 mm tubes. The transverse heat transfer coefficient increased with the decreasing pipe diameter under some conditions. In addition, this study also verified the adaptability of some existing correlations of R290.