降液管内液体混合的模拟计算

Simulation Calculation of Mixing in Downcomer

自五十年代末以来,塔板效率的模拟计算工作已有了长足的进展.但迄今的模拟工作都是在降液管内液体完全混合的假定下进行的.在大直径塔板上,由于液流不匀和二维返混,沿塔板出口堰的液体浓度是不相等的.由于假定液体在降液管内完全混合,则进入塔板的液体为均一的浓度,这对模型的求解和逐板计算都大为简便.八十年代初才见到Weiler和Lockett等关于降液管混合研究的报道.他们在矩形冷模装置上实测了降液管内液体的混合,并用涡流扩散模型求出了涡流扩散系数D’_e,证实在垂直方向上混合剧烈,可以为完全混合;但沿堰长则更接近于完全不混.工业上广泛应用弓形降液管的塔板,本研究在冷模塔弓形降液管内测得大量反映液体混合状态的数据,并运用混合池和涡流扩散两种模型,对降液管内的液体混合进行了模拟计算.

In this paper, simulation calculation of liquid mixing in downcomer is carried out by using eddy diffusion model and mixing pool model. The mixing quantity among pools and the eddy diffusivity De' expressing the mixing degree are obtained. The results indicate that mixing in downcomer is actually incomplete. It is a correction to the assumption of complete mixing in downcomer which is generally made in simulation calculations. The plate efficiency at various degrees of mixing in downcomer is calculated by the use of two-dimensional eddy diffusion model.