低温管路预冷过程两相流动与换热计算研究

Research on the Two-Phase Flow and Heat Transfer Characteristics of Cryogenic Pipeline Chill-Down Process

为揭示低温流体预冷管路过程中两相流动与换热特性,采用准稳态方法建立了低温管路预冷计算模型。该模型采用有限容积法来求解管内流体流动与换热方程,有限差分法求解管壁一维非稳态导热方程,流体与壁面的换热根据流型来判定选择对应的换热关联式,并对管壁外侧辐射漏热进行线性化离散处理。利用多组实验数据进行模型验证,结果表明模型对预冷时间预测的误差在10%之内。对预冷过程非稳态降温特性及流型与换热特性的计算结果表明:在低温流体预冷管路过程中,大部分换热方式为单相气强制对流和膜态沸腾,约占总预冷时间的95%,总换热量的75%,核态和过渡沸腾发生时间较短;预冷过程中存在一个最优质量流速,这既可以缩短预冷时间,同时可以减少推进剂的浪费。

To reveal the two-phase flow and heat transfer characteristics during the chill-down process of cryogenic fluid,a chill-down model was established with the quasi-steady-state method.In the model,the finite volume method was used to solve the fluid flow and heat transfer equation in the pipe,and the finite difference method was used to solve the one-dimensional unsteady heat transfer equation of the pipe wall.The heat transfer between fluid and the wall was calculated by appropriate heat transfer correlations,and the radiant heat in the pipe was linearized.The model was validated by the experimental data in literatures,and the results showed that the error of the model for chill-down time prediction is within 10%.The calculation results of the unsteady flow pattern and heat transfer characteristics of the chill-down process indicated that the single-phase gas forced convection and film boiling heat transfer occupy the most of chill-down process,accounting for about 95%of the total chill-down time and 75%of the total heat exchange flux.There is an optimal mass flow rate during the chill-down process,which can shorten the chill-down time and reduce the consumption of propellant.