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Approximations for unsteady state diffusion and adsorption with mass transfer resistance in both phases

机译:两相均具有传质阻力,用于非稳态扩散和吸附的近似值

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A new approximate kinetic model, valid for both long and short duration of transient mass (or heat) transfer processes, was proposed. The presented model may be used in the cases of transient diffusion in bodies in the shape of infinite slab, infinite cylinder or sphere. The case where mass transfer resistance is both inside and outside a body (adsorbent pellet) has been considered. In the presented model Laplace transform for diffusion equation is used, the solution is transformed to the form of continued fractions and the resulting expression is truncated to obtain such a number of terms that ensures the required accuracy. This concept, which was presented by J. Lee and D.H. Kim (Chemical Engineering Journal, 2012) for systems without external mass transfer resistance, in this work has been extended on systems where such resistance exists. On the basis of calculations done in this work it was shown that values obtained with the approximate model are almost identical to values derived from the exact model. It is worth mentioning that such consistency refers to all considered shapes regardless of the magnitude of external mass or heat transfer resistance. The model can be used for modelling and design of cyclic adsorption-desorption processes.
机译:提出了一种新的近似动力学模型,该模型对瞬态传质(或传热)过程的长时和短时都有效。所提出的模型可以用于无限大板,无限圆柱或球体形状的物体中的瞬时扩散情况。已经考虑了传质阻力既在体内又在体外(吸附剂颗粒)的情况。在所提出的模型中,使用了扩散方程式的拉普拉斯变换,将解变换为连续分数的形式,并截断了所得表达式以获得确保所需精度的大量项。这个概念是由J.Lee和D.H.Kim(化学工程杂志,2012年)提出的,适用于没有外部传质阻力的系统,这项工作已扩展到存在这种阻力的系统上。根据这项工作进行的计算,结果表明,用近似模型获得的值几乎与从精确模型得出的值相同。值得一提的是,这种一致性是指所有考虑的形状,与外部质量或传热阻力的大小无关。该模型可用于循环吸附-解吸过程的建模和设计。

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