受限空间小型急冷塔内喷雾蒸发的数值模拟

针对受限空间内小型急冷塔冷却水蒸发过程,运用计算流体力学(CFD)进行数值模拟,基于涡壳进气型急冷塔研究了喷嘴雾化粒径、喷射速度、喷射角度等喷嘴运行参数对急冷塔内蒸发过程的影响机制。结果表明:随着液滴粒径的增大,液滴蒸发时间、轴向以及径向蒸发距离均随之显著上升,粒径由40 μm增大至80 μm时蒸发时间增加了293%;当液滴喷射速度增加时,液滴的蒸发时间、轴向以及径向蒸发距离均有所下降,但增大至一定程度后其影响作用减弱;随着液滴喷射角度的增大,液滴蒸发时间及轴向蒸发距离减小,而径向蒸发距离无显著变化。因此,在急冷塔尺寸受限时选用70 μm以下的小雾化粒径喷嘴能够直接有效提升急冷塔的运行安全性。同时,与均匀进气型急冷塔相比,采用涡壳进气型急冷塔以及喷嘴成切圆布置方式能够在急冷塔上部形成湍流强化区域,喷嘴雾化粒径为80 μm时,轴向安全裕度可提升7%。该模拟结果可为小型化急冷塔的工程应用提供优化设计方案与运行指导参考。

NUMERICAL SIMULATION ON SPRAY EVAPORATION PROCESS FOR SMALL-SCALE QUENCH TOWER IN LIMITED SPACE

Aiming at small-scale quench tower in limited space, the effect of operation parameters of spray nozzle on the evaporation process was studied by using computational fluid dynamics (CFD), such as atomization droplet size, jet relocity and spray angle. The results showed that with the increase of the droplet size, the evaporation time, axial and radial evaporation distance of the droplet increased accordingly, and the evaporation time increased by 293% when droplet size increased from 40 μm to 80 μm. When the jet velocity of droplet increased, the evaporation time, axial and radial evaporation distance of the droplet decreased, but the effect was weakened when the jet velocity increased to a certain value. The increase of spray angle caused the decrease of the evaporation time and axial evaporation distance of the droplet, but there was no obvious trend on the radial evaporation distance. The small atomizing droplet size nozzle below 70 μm could directly and effectively improve the operation safety. By comparison, it was found that a turbulence intensified area was formed in the upper part of the quench tower with volute inlet, and that led to better cooling characteristic and operational safety than quench tower with upper vertical inlet, when the space of quench tower was limited. The axial safety margin could be increased by 7% with a droplet size of 80 μm. The simulation results could provide optimal design scheme and operation guidance for engineering application of miniaturized quench tower.