裂解吸热反应对乙烷超临界传热的影响

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。

Effects of Endothermic Cracking on Supercritical Heat Transfer of Ethane

Numerical simulation of supercritical heat transfer of ethane has been conducted.After comparing numerical results with and without pyrolysis,effects of ethane endothermic cracking on wall heat flux,bulk temperature,and Nusselt number variations were analyzed.With consideration of ethane pyrolysis,the ethane bulk temperature decreases 135 K while the wall heat flux increases twice at the tube outlet,supercritical heat transfer is improved,and the Nusselt number increases around 20%.For calculated cases,it is found that without pyrolysis,classical empirical heat transfer correlations are applicable with good accuracy,but with pyrolysis,the relative error between numerical and theoretical results increases.