连续液柱流自由表面非平衡绝热蒸发

分析连续液柱流自由表面绝热蒸发过程并进行了数值模拟,获得了汽液界面温度及蒸发通量分布规律。结果显示表面非平衡蒸发过程速率仅为按热力学平衡条件下最大理论计算量的20%,并且受液柱内部向自由表面传热控制。表面蒸发过程迅速衰减,当x/L=0.5,表面释放的蒸发热与液柱内部过热量之比水ηx(蒸发进程)仅为0.25,蒸发进程已接近尾声,揭示了强化液柱表面更新是强化该过程的主要因素。本模型计算结果得到了单液柱流绝热真空蒸发实验数据的验证,蒸发速率模拟值与实验值相对误差小于10%。

Adiabatic Non-equilibrium Evaporation from Free Surface of a Continuous Falling Liquid Cylindrical Column

Theoretical analysis of the adiabatical evaporation process from the free surface of a continuous falling liquid cylindrical column was carried out.The axial distribution of temperature on the vpaor-liquid interface and evaporation flux were obtained numerically.It was shown that the rate of this non-equilibrium surface evaporation accountes for only 20% of the theoretical maximum calculated under thermodynamic equilibrium.The evaporation rate is controlled by heat transfer from the inner of the liquid cylindrical column.The evaporation rate attenuates rapidly along the flow direction.When x/L=0.5,the evaporation progress ηx is only around 0.25,which means that the evaporation is coming to the end.It revealed that the refreshment on the surface of liquid is the key to intensify the surface evaporation process.The simulation results of this model were verified by the experimental data of the adiabatic vacuum evaporation from the free surface of a continuous falling liquid cylindrical column,with an error within 10%.