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Age distribution in the kenics static micromixer with convection and diffusion / Minye Liu in Industrial & engineering chemistry research, Vol. 51 N° 20 (Mai 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 20 (Mai 2012) . - pp. 7081-7094 Titre : Age distribution in the kenics static micromixer with convection and diffusion Type de document : texte imprimé Auteurs : Minye Liu, Auteur Année de publication : 2012 Article en page(s) : pp. 7081-7094 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Diffusion  Convection  Micromixing Résumé : Age distribution in a Kenics static micromixer is studied by mean age solution of a steady transport equation. The spatial distribution of mean age reveals locations of older material that could potentially cause process fouling and product defects. At the microscales of the mixer, both convection and diffusion strongly affect age distribution. A method is developed to compute an average effective diffusivity to measure false diffusion due to numerical errors. The range of Peclet number is found so that the scalar solution is not affected by false diffusion. The effect of convection and diffusion is studied for Re numbers that cover the full range of laminar flows in the mixer. Diffusion broadening is found to have a strong effect on the striation structures in the mixer. Age distribution in the mixer is quantitatively measured with a frequency distribution function and two different variances, the variance of residence time and the variance of mean age. It is found that the mean age variance decay rate increases almost monotonically as Re increases. It is shown that the distribution of mean age is always narrower than that of residence time. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25925050 [article] Age distribution in the kenics static micromixer with convection and diffusion [texte imprimé] / Minye Liu, Auteur . - 2012 . - pp. 7081-7094. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 20 (Mai 2012) . - pp. 7081-7094 Mots-clés : Diffusion  Convection  Micromixing Résumé : Age distribution in a Kenics static micromixer is studied by mean age solution of a steady transport equation. The spatial distribution of mean age reveals locations of older material that could potentially cause process fouling and product defects. At the microscales of the mixer, both convection and diffusion strongly affect age distribution. A method is developed to compute an average effective diffusivity to measure false diffusion due to numerical errors. The range of Peclet number is found so that the scalar solution is not affected by false diffusion. The effect of convection and diffusion is studied for Re numbers that cover the full range of laminar flows in the mixer. Diffusion broadening is found to have a strong effect on the striation structures in the mixer. Age distribution in the mixer is quantitatively measured with a frequency distribution function and two different variances, the variance of residence time and the variance of mean age. It is found that the mean age variance decay rate increases almost monotonically as Re increases. It is shown that the distribution of mean age is always narrower than that of residence time. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25925050

Prediction of tracer concentration and mixing in CFSTRs with mean age distribution / Minye Liu in Industrial & engineering chemistry research, Vol. 50 N° 9 (Mai 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 9 (Mai 2011) . - pp. 5838-5851 Titre : Prediction of tracer concentration and mixing in CFSTRs with mean age distribution Type de document : texte imprimé Auteurs : Minye Liu, Auteur Année de publication : 2011 Article en page(s) : pp. 5838-5851 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Mixing  Tracers  Prediction Résumé : Three-dimensional time-dependent tracer concentration distributions in nonideal continuous flow stirred tank reactors with pulse input are studied computationally. Both the steady transport equation for mean age and the time-dependent transport equation for tracer concentration are solved. It is found that the time-dependent tracer concentration history can be divided into two stages: an initial stage, in which the concentration is highly location-dependent, and a stationary stage, in which the concentration decays with a location-independent, constant exponential rate. This rate is found to be the inverse of the volume-averaged mean age. The length of the initial stage is found to be very short, on the same order of magnitude as the batch blend time. It is also found that the scaled concentration distribution in the stationary stage is almost identical to the scaled mean age distribution. The spatial and temporal concentration distribution in the stationary stage can be determined once the initial stage and the mean age solution are obtained. Thus, the CPU time required is orders of magnitude smaller than that for the full time integration of the unsteady concentration equation. With the solution of tracer concentration distribution known, mixing time and other quantitative measures for the tracer mixing can be easily calculated. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24128710 [article] Prediction of tracer concentration and mixing in CFSTRs with mean age distribution [texte imprimé] / Minye Liu, Auteur . - 2011 . - pp. 5838-5851. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 9 (Mai 2011) . - pp. 5838-5851 Mots-clés : Mixing  Tracers  Prediction Résumé : Three-dimensional time-dependent tracer concentration distributions in nonideal continuous flow stirred tank reactors with pulse input are studied computationally. Both the steady transport equation for mean age and the time-dependent transport equation for tracer concentration are solved. It is found that the time-dependent tracer concentration history can be divided into two stages: an initial stage, in which the concentration is highly location-dependent, and a stationary stage, in which the concentration decays with a location-independent, constant exponential rate. This rate is found to be the inverse of the volume-averaged mean age. The length of the initial stage is found to be very short, on the same order of magnitude as the batch blend time. It is also found that the scaled concentration distribution in the stationary stage is almost identical to the scaled mean age distribution. The spatial and temporal concentration distribution in the stationary stage can be determined once the initial stage and the mean age solution are obtained. Thus, the CPU time required is orders of magnitude smaller than that for the full time integration of the unsteady concentration equation. With the solution of tracer concentration distribution known, mixing time and other quantitative measures for the tracer mixing can be easily calculated. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24128710