超临界压力下低温甲烷的湍流传热数值研究

Numerical investigation of turbulent heat transfer of cryogenic-propellant methane under supercritical pressures

关键词:  低温甲烷  超临界压力  对流换热  数值模拟

Key words:  Cryogenic methane  Supercritical pressure  Convection heat transfer  Numerical simulation

摘要:

通过系统的数值模拟计算,在准确确定甲烷的热力学和传输物性变化的情况下,详细分析了两种热流密度下超临界压力对低温甲烷的湍流传热过程的影响,揭示了对流换热Nusselt数的变化规律。计算结果表明:在超临界压力下,热力学和传输物性对湍流传热现象会造成很大的影响,尤其在甲烷的临界区域附近,由于物性的剧烈变化会导致传热过程的恶化现象;在高热流密度情况下(如7MW/m2),增大管内压力有利于提高对流换热强度;现有的常用变物性湍流传热公式不能适用于超临界压力下低温甲烷的对流换热计算。

Abstract:

A numerical investigation,incorporating an accurate estimation of the thermodynamic and transport properties of methane,was systematically conducted for elucidating turbulent convective heat transfer phenomena and the corresponding Nusselt number variation with cryogenic-propellant methane flowing under supercritical pressures with two different wall heat fluxes.Numerical results indicate that under supercritical pressures,the variations of thermophysical properties produce significant effects on turbulent heat transfer.Particularly in the critical region of methane,drastic property variations result in heat transfer deterioration.At a high wall heat flux,i.e.7 MW/m2,the heat transfer coefficient is improved with increasing pressure under supercritical conditions.The conventional heat transfer formula,although considering property variations,cannot be applied directly to calculate turbulent heat transfer coefficient of cryogenic-propellant methane under supercritical pressures.