垂直上升圆管内超临界航空煤油的传热恶化数值研究

Numerical Study on Heat Transfer Deterioration of Supercritical Aviation Kerosene in Vertical Upward Circular Tubes

关键词:  超临界压力  航空煤油  传热恶化  数值研究

Key words:  Supercritical pressure  Aviation kerosene  Heat transfer deterioration    Numerical study

摘要:

采用RNG k-ε湍流模型结合增强壁面处理的方法以及10组分替代模型对RP-3航空煤油在垂直上升圆管内的超临界对流换热进行了数值研究。详细分析了超临界条件下航空煤油的传热恶化机理，并将数值计算结果与常用经验换热公式值进行了比较，以考察这些经验关系式的适用性。计算结果表明:在较高的热流密度下，热物性的剧烈变化使径向流场产生异变，引发了复杂的传热恶化现象。其中，低主流焓值区的传热恶化是由热加速作用导致的，高主流焓值区的传热恶化是由径向速度波动造成的。Bae-Kim关系式能较好地反映垂直上升圆管中航空煤油的超临界传热情况，预测值与模拟值的相对误差均在20%以内；而Bishop等给出的经验公式则不再适用。

Abstract:

Numerical study on supercritical convective heat transfer of RP-3 aviation kerosene in vertical upward circular tubes has been carried out，based on the RNG k-ε turbulence model with enhanced wall treatment，and a 10-species kerosene surrogate model. The heat transfer deterioration mechanisms of aviation kerosene under supercritical conditions were analyzed in detail. Moreover，the numerical results have been compared with several conventional empirical heat transfer formulae to investigate the applicability of these expressions. Results indicate that under relatively high heat fluxes，the abrupt thermophysical properties variations significantly modify the radial flow fields，leading further to complex heat transfer deterioration phenomena. The heat transfer deterioration in the low bulk enthalpy region is caused by thermal acceleration，whereas the heat transfer deterioration in the high bulk enthalpy region is due to the radial velocity oscillation. The Bae-Kim formula can be better used for supercritical heat transfer predictions of aviation kerosene in vertical upward circular tubes. The relative errors between the predicted values and numerical results are generally within 20%，while the empirical expression proposed by Bishop et al. is no longer applicable.