Elements for Real Time Teady Simulation for Flat Glass Lehr Control

Abstract

In partnership with Ford/Visteon, Sandia National Laboratories began work on design and implementation of improved end-to-end control for float glass production, under DOE Office of Industrial Technology sponsorship. The first task undertaken was to provide an intelligent control for the annealing lehr, both for optimum usage of sensors and for the ability to report digitally the state of the lehr to an end-to-end control system. The heat transfer simulation of the lehr enclosure for that purpose is described here. This includes a closed-form solution for the infinitely wide glass ribbon, which allow robust computations of the thermal profile and inverses of this function for controls use. This also allows useful initial temperature estimates for the case with counterflow in the lehr ducts, which should greatly simplify and speed the convergence of more detailed models in which the glass participates in the radiative exchanges. This is supplemented by software to compute radiative viewfactors of lehr elements for use in finite-width versions of the simulation. A brief discussion of how stresses could be computed from such a thermal solution is given, but not implemented in software.-4 - ACKNOWLEDGEMENTS