毛细管内气-液Taylor流动换热特性数值模拟

Numerical investigation on heat transfer and hydrodynamic characteristics of gas-liquid Taylor flow in capillaries

采用动网格技术,对恒壁温边界下,竖直上升毛细管(管径为1mm)内充分发展状态的气-液Taylor流动进行数值研究,分析入口雷诺数、气泡体积分数对Taylor流动的换热阻力特性的影响.模拟结果表明,由于Taylor气泡的存在,液柱区域的摩擦阻力因子高于单相流动,模拟结果与经验公式吻合较好.液柱表观努赛尔特数随气泡体积分数的增大而增大,基本不随入口雷诺数的变化而改变.在恒壁温边界下,Taylor气泡及液膜区域对整体传热的贡献较小.液柱区域内循环可以提高加强核心区域与近壁面区域的热量交换,加快换热过程,提高Taylor流动的传热效果.内循环对换热的强化作用随着液柱长度的增大而降低.

Numerical work of fully developed gas-liquid Taylor flow in vertical upward capillaries with inner diameter of 1mm under isothermal wall boundary condition was performed with the dynamic mesh model.The effects of inlet Reynolds number and gas void fraction on thermal and flow characteristics of Taylor flow were discussed.Results indicate that the friction factor in the liquid slug is higher than that of singlephase flow,and the empirical correlation can predict the numerical data well.The apparent liquid slug Nusselt number increasing with increasing gas void fraction and remains nearly constant with increasing inlet Reynolds number.The Taylor bubble and the thin liquid film region have insignificant contribution to the overall heat transfer coefficients in Taylor flow under isothermal wall boundary condition.The inner recirculation in the liquid slug region can improve the heat transfer between the tube wall and the core region,accelerate the heat transfer process,and enhance the heat transfer performance in Taylor flow.The effect of inner recirculation on heat transfer enhancement decreases with increasing liquid slug length.