0.5mm毛细管内气-液Taylor流动换热数值研究

Numerical study of hydrodynamic and heat transfer characteristics of gas-liquid Taylor flow in a 0.5mm capillary

采用移动计算域方法研究0.5mm毛细管内充分发展的气液Taylor流动换热特性,分析了Taylor气泡的形状、压降与换热特性。结果表明,随着入口Reynolds数Re的增大,气泡尾部的不稳定区域增大,液膜厚度逐渐增大,气泡长度变长;随着气泡体积分数ξg的增大,气泡形状基本不变而长度逐渐增大。阻力因子f随Re、ξg增大而降低,两相阻力系数高于单相的情况。平均Nusselt数Nutp随Re增大而增大,增大趋势逐渐降低;随ξg增大而线性降低。Taylor流的Nutp为单相的1.23倍,强化换热效果。

The hydrodynamic and heat transfer characteristics of the fully-developed gas-liquid Taylor flow in a 0.5 mm capillary were studied numerically using the moving frame method.The bubble shapes,pressure drops and heat transfer characteristics were analyzed.The numerical results show that the liquid film thickness,the bubble length and the length of the unsteady region near the bubble tail increase with increasing Re.The effect of void fractionξgon the bubble shapes is insignificant,while a longer bubble is expected at a higher ξ_g.The frictional factor f which is higher than the single-phase flow decreases with increasing Re and ξ_g.The average Nusselt number increases with increasing Re,while the increasing trend decreases with increasing Re.Nutpdecreases linearly with increases inξgand Nutpis about 1.2to 3times of that for the single-phase flow which means that Taylor flow can enhance heat transfer.