摘要
本文将宏观混和与微观混和看成是两种不同尺度的体积增长过程,着重考虑二者之间的相互作用及其在混和中的不同地位。分析表明,在某一特征时间 t_c 之前微观混和占主导地位,而随后则宏观混和起主要作用。于是可将无限尺度上的混和过程划分为三个区域,每一个区域的物料分别处于完全离集、部分离集和最大混和状态。对于有限尺度容器中的混和,则可以划分为两种类型:一种由整体到局部,另一种由局部到整体。对于化学反应器中的混和,则可根据反应的快慢而进一步分成5种不同的情况。
Macromixing and micromixing can be regarded as two volume growth processes at different scales.The interaction between macro-and micromixing was investigated in this paper.It is shown that the growth of the micromixing zone will overtake that of macromixing zone at a characteristic time t_c,which is given by the following equation (4πln10)UDe t_c^2=qt_s+10(v/ε)^(1/2)q{exp[0.1(ε/v)^(1/2)(t_c-t_s)]-1} Before t=t_c,micromixing is dominant and after that macromixing will control the mixing process.The infinite mixing field can thus be divided into three regions,corresponding to the state of complete segregation,partial segregation and maximum maxedness respectively.For the mixing vessel with finite size,the development of the mixing zones will be confined by the vessel,resulting in two mixing ways:homogenization from the globul region to the local districts and that from the local districts to the globul region.When chemical reactions exist,mixing types can be further sub- divided into the five cases according to the relative rates of mixing and chemical reaction.
出处
《化学反应工程与工艺》
CAS
CSCD
北大核心
1990年第4期23-29,共7页
Chemical Reaction Engineering and Technology
基金
国家自然科学基金(1880364)
