降膜吸收CO_(2)水平管外滴状流的脉动特性数值模拟

Numerical simulation of pulsation characteristics of droplet model flow falling film absorbing CO_(2) outside the horizontal tubes

液滴的瞬态行为对强化水平管降膜吸收CO_(2)装置的性能至关重要。基于VOF(volume of fluid)方法建立了滴状流降膜吸收CO_(2)的二维模型,引入液滴下坠长度与无量纲时间来分析滴状流降膜吸收CO_(2)过程中的液滴脉动与管间距和雷诺数Re的关系。结果表明:液体在换热管下侧堆积直至形成液滴的过程中,受到重力、表面张力与惯性的相互作用,液滴的移动方向出现了多次反转;液滴脉动过程中,由于摩擦阻力的存在,随着无量纲时间的增加,液滴脉动幅度逐渐减小;由于管间距的增加提高了液滴在换热管底部交汇时的动能,导致随着管间距的增加,液滴的脉动次数与脉动幅度逐渐增加;在Re不断增加的情况下,液滴滴落速度的减小导致液滴的脉动次数与幅度也逐渐减小。

The transient behavior of liquid droplets was crucial for enhancing the thermal performance of the horizontal falling film CO_(2) absorbers.A two-dimensional mathematical model of the droplet model flow falling film absorbing CO_(2) was established based on the volume of fluid(VOF)method.The effects of the Reynolds number Re and the tube spacing on the droplet pulsation in the process of the falling film absorbing CO_(2) were analyzed by introducing the drop length and the dimensionless time.The results showed that in the period of the formation for liquid droplets at the bottom of tubes,affected by the gravity,surface tension and inertia,it could be found that there were several reversals in the movement direction of liquid droplets.During the period of the droplet pulsation,due to the frictional resistance,the pulsation amplitude gradually decreased with respect to the dimensionless time.The kinetic energy of droplets increased with the tube spacing increasing when the liquid accumulated at the bottom of tubes,resulting in an increase in both the amplitude and number of pulsation.The amplitude and number of pulsation decreased with the increase of Re due to the droplet velocity decreasing.