生长管中过饱和度在不同构建方式下的分布特性

Distribution characteristics of supersaturation from different creating methods in growth tube

为了研究水汽相变中不同构建方式形成的细颗粒长大所需的过饱和环境,利用变物性参数传热传质模型对生长管中过饱和度水平进行了预测,并评价了2种过饱和构建方式:低温饱和气流与高温热水相接触(方式1);高温饱和气流与低温冷水相接触(方式2).同时分析了进气温度、管壁水温度、进气流速和压力对2种构建方式下所得过饱和度的影响.结果表明:变物性与定物性参数下预测过饱和水平有一定的差异性,最大差异性体现在生长管中心线处;方式2获得的过饱和分布较为均匀;气流与水温差较低时,方式1所得平均过饱和度大;温差较高时,方式2所得平均过饱和度大;温差相同时,较低的温度水平更有利于提高生长管中过饱和水平;压力和进气流速的增加有利于生长管过饱和水平均匀化.

To study the supersaturation environment for fine particle enlargement in vapor phase transition,which is formed from different creating methods,the supersaturation level is predicted in the growth tube by the heat and mass transfer model with variable physical parameters. Two methods that saturated cooled air flowmeets with warm water（ method 1） and saturated warm air flowmeets with cooled water（ method 2） are estimated. The influences of the inlet flowtemperature,the wall water temperature,the inlet flowrate and the pressure on the supersaturation by the creating methods are analyzed. The results demonstrate that there is a difference in the prediction of supersaturation level with variable and constant physical parameters,and the maximum difference is in the center of the growth tube. The supersaturation distribution obtained from method 2 is more uniform. With a small temperature difference between the inlet flowand the wall water,the average degree of the supersaturation obtained from method 1 is higher. With a large temperature difference,the average degree of the supersaturation obtained from method 2 is higher. With an equal temperature difference,lowtemperature is positive to promote the supersaturation level in the growth tube. The increase of the pressure and the inlet flowrate is in favor of homogenization of the supersaturation level in the growth tube.