Residence Time Distribution (RTD) theory is revisited and tracer technology discussed. The background of RTD following Danckwerts ideas is presented by introducing “distribution” functions for residence time, internal age and intensity function and how to experimentally obtain them with tracer techniques (curves C and F of Danckwerts). Compartment models to describe fluid flow in real reactors are reviewed and progressive modeling of chromatographic processes discussed in some detail. The shortcomings of Standard Dispersion Model (SDM) are addressed, the Taylor-Aris model discussed and the Wave Model of Westerterp’s group introduced. The contribution of Computational Fluid Dynamics (CFD) is highlighted to calculate RTD from momentum and mass transport equations and to access spatial age distribution and degree of mixing. Finally smart RTD and future challenges are discussed.

中文翻译：

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重新审视停留时间分布 (RTD)

重新审视了停留时间分布 (RTD) 理论并讨论了示踪技术。通过介绍停留时间、内部年龄和强度函数的“分布”函数以及如何使用示踪技术（Danckwerts 的曲线 C 和 F）通过实验获得它们，介绍了遵循 Danckwerts 思想的 RTD 的背景。回顾了描述真实反应器中流体流动的隔室模型，并详细讨论了色谱过程的渐进式建模。解决了标准色散模型 (SDM) 的缺点，讨论了 Taylor-Aris 模型并介绍了 Westerterp 小组的 Wave 模型。计算流体动力学 (CFD) 的贡献被突出显示，以根据动量和质量传输方程计算 RTD，并访问空间年龄分布和混合程度。