微通道内低黏聚合物流体的停留时间分布研究

Research on residence time distribution of the low-viscous polymer fluid in microchannel

以低分子量的聚丙二醇为流动介质、酸性橙的N,N-二甲基乙酰胺溶液为示踪剂,采用脉冲响应法测定了螺旋型微通道(MC)反应器内的停留时间分布(RTD),验证了平行多釜串联(PTIS)模型与RTD实验数据的匹配性,系统考察了MC长度和Reynolds数(Re)对RTD的影响,并讨论了流体径向速度分布指数y和Peclet数(Pe)的变化规律。结果表明,RTD随MC长度的增加而变窄。当通过降低黏度来增大Re时,RTD随之变窄。当通过增大流速来增大Re时,若管径较大,则RTD随之变窄。但若管径较小且管长不长时,则RTD随Re的增加而变宽;如管长较长,则RTD随Re(或流速)的增加先变宽后变窄,即存在临界Reynolds数(Rec)。RTD的这些变化规律表明,二次流动和径向分子扩散对细小管径的MC的RTD有显著的影响。

Residence time distribution (RTD) in the spiral microchannel (MC) was determined by the impulse response method using polypropylene glycol with low molecular weight as the fluid carrier and N,N-dimethylmethylacetamide solution of acid orange as the tracer.The fittingness between parallel tanks-in-series(PTIS) model and RTD experimental data was verified.The influence of MC’s length and Reynolds number (Re) on RTD was systematically studied.Additionally,the change law of radial velocity index y and Peclet number (Pe) of the fluid was thoroughly discussed.The results indicated that RTD became narrower with the increase of MC’s length.When Re was increased by reducing viscosity,RTD became narrowed with Re increasing.When Re was increased by increasing flow rate,RTD would also become narrower as Re grew if the MC’s diameter was large.However,if the MC’s diameter was small and length was short,RTD would be widened as Re increased;on condition of longer length,RTD could become widened first and then narrowed with the increase of Re (or velocity).That is,there was a critical Reynolds number (Rec).These changes of RTD indicate that secondary flow and radial molecular diffusion have a significant effect on the RTD of MC with small diameters.