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本文对圆管内超临界状态下乙烷的湍流传热过程进行了数值模拟,分析了乙烷高温裂解对壁面热流密度、平均温度以及对流换热Nusselt数的影响。计算结果表明:考虑乙烷高温裂解吸热反应,管内平均温度会降低,出口处温度降低可达135 K;壁面热流密度则会显著增加,热出口处可增加近2倍;热裂解反应改善了超临界对流换热效果,Nusselt数可提高约20%。在本文计算条件下,经典的对流换热关系式可准确适用于不考虑热裂解反应的情况,而对于考虑裂解吸热反应的超临界乙烷传热情况则误差较大。
In this paper, the turbulent heat transfer of ethane in a supercritical state in a circular tube was numerically simulated. The effects of ethane pyrolysis on wall heat flux, average temperature and convective heat transfer Nusselt number were analyzed. The calculation results show that considering the endothermic reaction of ethane pyrolysis at high temperature, the average temperature in the tube will decrease, the outlet temperature will decrease to 135 K, the wall heat flux will increase significantly, and the heat outlet may increase nearly two times. Supercritical convection heat transfer effect, Nusselt number can be increased by about 20%. Under the condition of this calculation, the classical convective heat transfer equation can be accurately applied to the situation without considering the pyrolysis reaction, while the error of the supercritical ethane heat transfer with considering the endothermic cracking reaction is relatively large.