On Axial Diffusion in Laminar-Flow Reactors

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• 作者：E. Bruce Nauman and Ashish Nigam
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2005
• 出版时间：July 6, 2005
• 年：2005
• 卷：44
• 期：14
• 页码：5031 - 5035
• 全文大小：117K
• 年卷期：v.44,no.14(July 6, 2005)
• ISSN：1520-5045

文摘

Although unimportant in conventional laminar-flow reactors, axial diffusion can be the dominantmechanism for mixing in micrometer-scale devices. The low Reynolds numbers characteristic ofthese devices allow numerical solution of the convective diffusion equation, coupled whennecessary with the equations of motion. The method of false transients provides a simple wayto obtain such numerical solutions. For the case of reaction within a confined zone, there is aninternal optimum with respect to diffusion. Unlike the lumped-parameter axial dispersion model,the conversion and residence time distribution depend on the boundary conditions. The physicallyrealizable open-open boundary conditions give higher conversions and more uniform residencetimes. Micrometer-scale devices will have such high levels of diffusion that mixing betweenseparately fed, compatible components will become trivially easy. Reactor performance willapproximate that of a CSTR with attendant low yields and poor selectivities.