压力对超临界碳氢燃料换热恶化影响的数值研究

Numerical Study of Pressure Effect on Deterioration in Heat Transfer with Supercritical Hydrocarbon Fuel

为了研究竖直管道内压力对超临界碳氢燃料换热恶化的影响,采用数值模拟的方法,选择RP-3的四组分替代模型和LS低雷诺数湍流模型,分别从浮升力和物性的角度深入分析压力作用机理,并对比了直径2mm与10mm管道内压力的作用效果。各工况下计算结果与实验数据基本吻合,证实了计算方法的准确性。数值模拟结果表明:不考虑裂解结焦的情况下,系统压力超过5MPa后,碳氢燃料物性随温度变化趋于平缓,密度及比热容在管内不均匀性得到改善,同时壁面附近比热容平均值增大,使得管内换热恶化得到有效缓解;而在直径10mm管道内,热流从壁面到主流区传播减慢,管壁与管道轴心处流体温差最大可达300K,物性不均匀现象加剧,增大压力对换热恶化的缓解效果被削弱。

In order to study the pressure effect on heat transfer deterioration of supercritical hydrocarbon fu- el in vertical tube, numerical method with four component surrogate model of RP-3 and LS low Reynolds turbu- lence model was carried out, buoyancy force and physical properties were focused to analyze mechanism of pres- sure effect, meanwhile comparisons between pipes of diameter 2mm and 10mm were done. The numerical results on wall temperature distribution under various conditions were compared with experimental data and a good agree- ment was obtained. Results of the research suggest that when pressure increase to 5MPa without concerning de- composition and coking, the change of physical properties tends to be gentle, the inhomogeneity of density and specific heat are alleviated, average of specific heat increases as well, which all make heat transfer deteriora- tion alleviated. But in the pipe of diameter 10mm, fluid inside is harder to be heated and temperature difference between pipe wall and pipe axis is up to 300K, which leads to the increase of property inhomogeneity, pressure effect of alleviating heat transfer deterioration is weakened.