Mean Age Theory in Continuous Casting Tundish

Abstract

Mean age theory is introduced to characterize the mixing performance of tundish based on the spatial distribution of tracer’s mean age. Conventional residence time distribution theory was widely used in the tundish analysis; however, it contains no information of the local mixing states. Based on mean age distribution, melt change efficiency is defined as a performance index to evaluate how quickly the old melt in the tundish can be replaced by the young melt from the ladle. Case studies, divided into three groups, were carried out to test the applicability of the new theory in a single-strand tundish with flow control devices of weir, dam and turbulence inhibitor. The developed mean age model was well validated by comparison with measurement in water model and computational fluid dynamics (CFD) results using residence time distribution (RTD) model. Mean age model can reduce the computing time to two orders of magnitude less in comparison with conventional transient RTD model, which improves the feasibility of CFD modelling in parameter studies to a broader extent.

CFD-Based Compartment Modeling of Continuous Polymer Reactors in Milli-Structured Apparatuses by Use of the Mean Age Theory

“…The mean age theory applies the concept of the residence time distribution (RTD) to every single point in the domain and the mean age identifies with high local values potential fouling zones. Due to steady-state simulations, the mean age theory offers an efficient way to analyze the fluid dynamics and mixing characteristics, which has already been applied to continuous problems, e.g., continuous flow stirred tank reactors, − static micromixers, or casting tundishes . Gresch et al already defined a parameter for the age to derive a CPT model of a simple flow reactor before the mean age theory was published by dividing the domain by iso-surfaces of the age parameter .…”

“…Due to steady-state simulations, the mean age theory offers an efficient way to analyze the fluid dynamics and mixing characteristics, which has already been applied to continuous problems, e.g., continuous flow stirred tank reactors, 25−28 static micromixers, 29 or casting tundishes. 30 Gresch et al already defined a parameter for the age to derive a CPT model of a simple flow reactor before the mean age theory was published by dividing the domain by iso-surfaces of the age parameter. 9 The flow and mean age field of a complex reactor geometry with static mixing elements in this contribution are more complex, and the method would merge potential fouling zones into the main flow so that there is a limited spatial interpretation.…”

Application of Mean Age Theory in Multi-strand Tundish

“…To address this issue, a new theory based on the steady-state spatial distribution of mean age was proposed to analyze the flow patterns in a single-strand tundish. 16) The mean age is defined as the average time of all materials passing through a given location in a continuous system. 17) The mean age is governed by a passive scalar transport equation, which can be solved by using a CFD code.…”

An Integrated Workflow for Designing a Single-strand Tundish Using CFD-Taguchi Method and Mean Age Theory

“…To overcome these limitations, a new theory based on the mean age distributions was recently introduced to characterize the tundish's mixing performance. 20) This theory was originally used for mixing characterization in the chemical reactors, proposed by Danckwerts in 1958. 21) Mean age of the melt in tundish is defined as a passive scalar that can be solved under steadystate conditions.…”