Technical Papers and Presentations

Bi2Sr2CaCu2O8+δ (Bi 2212) is being developed as a high temperature superconductor (HTS) technology with practical use in ultra-high field (+30 T) magnets. A critical processing step for this conductor is a ~890 degC heat treatment at elevated pressure (~50 atm). The reaction of this superconductor involves an exhaust of oxygen during the melting phase followed by an uptake of oxygen during the freezing phase of the reaction. This demands the furnace be an open system, flowing gas to flush and replenish the required oxygen balance throughout the heat treatment. Therefore, the modeling of an overpressure furnace used for this reaction has become a critical tool in understanding the furnace’s performance, improving design features, and putting forth a plan to scale up our facilities to an even larger reaction furnace.

Focused finite element modeling (FEM) efforts study the non-isothermal flow established within the furnace. Appropriate boundary conditions reflect the operation of the actual hardware on the furnace, and the materials selections are made to best study the thermal lag of the furnace, ultimately limited by the thermal diffusivities of all of the furnace components. Strong natural convection loops are shown to govern the heat transfer and temperature homogeneity of the furnace, and clever manipulation of the flow has led to significant improvements to the furnace performance. The CFD (Non-Isothermal Laminar Flow) and Heat Transfer modules of COMSOL Multiphysics^® simulation software proved very useful.