上升管内超临界CO_(2)/丙烷混合物传热特性研究

Study on Heat Transfer Characteristics of Supercritical CO_(2)/Propane Mixtures in Upward Pipe

采用变普朗特数模型对超临界CO_(2)/丙烷混合物在垂直上升管内的传热特性进行数值分析。混合物中丙烷的质量分数为0∼15%(ω=0∼15%)。ω从0%增加到10%时,平均换热系数升高,壁温峰值逐渐减小且沿流动方向向后移动,局部传热恶化得到改善。ω=15%时,壁温单调增加传热恶化消失。丙烷对壁温的影响随着进口温度和热流密度的减小而逐渐增大。T_(in)=285∼290 K范围内,CO_(2)和CO_(2)/丙烷混合物(ω=5%)的壁温峰值分别变化20 K和2 K,而传热系数谷值的最大变化为6.1%和1%。此外在G=500 kg·m^(−2)·s^(−1)、T_(in)=285∼295 K、q=50∼70 kW·m^(−2)宽工况范围内,提出用于CO_(2)/丙烷混合物(ω=0∼15%)的传热预测关联式,关联式的误差在±20%内。

The heat transfer characteristics of supercritical CO_(2)/propane mixtures in a vertical upward tube were numerically analyzed using variable turbulent Prandtl number model.The mass fractions of propane in the mixtures were 0∼15%(ω=0∼15%).Asωincreases from 0%to 10%,the average heat transfer coefficient increases while the peak wall temperature gradually decreases and moves backwards in the flow direction.The localized heat transfer deterioration is improved.Whenω=15%,the wall temperature increases monotonously and the heat transfer deterioration disappears.The effect of propane on wall temperature gradually increases with decreasing inlet temperature and heat flux.In the range of T_(in)=285∼290 K,the peak wall temperatures of CO_(2)and CO_(2)/propane mixtures(ω=5%)varied by 20 K and 2 K,respectively,while the maximum variations of the heat transfer coefficient valleys are 6.1%and 1%,respectively.In addition,in the wide operating range of G=500 kg·m^(−2)·s^(−1),T_(in)=285∼295 K and q=50∼70 kW·m^(−2),a correlation for predicting the heat transfer of CO_(2)/propane mixtures(ω=0∼15%)was proposed.The error of the correlation is within±20%.