Numerical Simulation Of Heat Transfer And Tin Penetration In The Float Process

Tin bath is the main equipment for plate glass formation, the temperature controlof float glass tin bath has important significance on both the glass quality and energyconsumption. The detailed temperature field obtaining by numerical simulation is thepremise of the preset and on-line control for the operation parameters. But the existingresearches always focus on the sub-models, the overall performance of the whole tinbath cannot be analyzed. Meanwhile, there is no general complete numerical technologyfor the analysis of various factors on tin penetration which is the inherent defects offloat process. In the present thesis, the heat transfer and tin penetration in the floatprocess are systematically studied, and the simulation of whole tin bath is carried out.The radiative transfer coefficient between the heater and the glass ribbon iscalculated by Monte Carlo method. The overall economic loss which can balance thecontrol quality and energy consumption economically is proposed. The optimizedpower distribution is obtained by numerical simulation, with which the temperaturefield is improved while the electricity input is reduced.The moving surface of glass melt is tracked and reconstructed at the tin bathentrance using PLIC method. It is found that part of the glass melt moves toward theupstream, and stagnant glass melt which affect the uniformity is formed. When theslope of the lip brick is smaller, less glass melt is stagnated. The velocity andtemperature fields of protective gas and molten tin are simulated. Back flow and vortexare found in the top half atmosphere. The back flow is more obvious under largerdragging velocity of glass ribbon. The temperature of gas near the heating (cooling)components is heated (cooled) significantly. Back flow is also observed in the bottomhalf molten tin and near the edge of tin bath which is not covered by the glass ribbon.There exists a large lateral temperature difference at the surface of molten tin. Effectivetemperature difference is defined to evaluate the overall lateral temperature differenceof molten tin. The optimal linear motor's output and working direction are found tominimize the effective temperature difference. Based on the simulation and analysis ofthe sub-models, the whole tin bath model and its simulation methods are set up. A realtin bath is simulated and the results match with the experimental ones. The stannic ions' diffusion process is simulated by molecular dynamics. It is foundthat temperature has a great impact on stannic ions' diffusion coefficient. The diffusioncoefficient increases with the increasing sodium content, while larger calcium rationwill reduce the stannic ion's diffusion coefficient. The tin penetration characteristics aremeasured by XRF and XPS methods, and they are set as the boundary conditions for tinpenetration simulation. Combining float glass forming process, the coupled tinpenetration simulation method is developed. The influences of different factors on thetin penetration process are analyzed by the coupled simulation method. The resultshows that the satellite peak exists in the high iron glass' tin penetration profile, whilethere is no such phenomenon in the low iron glass because of unobvious accumulationeffect of stannic ion. When float time increases, both the tin penetration profile and thesatellite peak drift to a greater depth in the glass. The amount of penetrated tin increaseswith increased tin bath entrance width.Finally, the float glass numerical simulation software is developed based on themain numerical technologies for the temperature field and tin penetration simulation.Other auxiliary functions are also supplied in the software.