The NPL software packages TherMOL 3D and MTDATA have been successfully linked to provide a powerful software system capable of modelling transient heat transfer, taking account of changes in material properties with changes in temperature and phase. The new hybrid software is also able to model complex multi-material structures subjected to various heat transfer boundary conditions.

Simulations for both the hybrid software and the original TherMOL 3D software were run for a steel block subjected to constant temperature heating. Figure 1 shows predicted curves of temperature against time obtained near the surface of the slab. The hybrid model predicts a slower increase in heating as it can take account of the changing heat capacity of the material, whilst the sharp change in gradient at about 10 seconds is as a result of the material changing from the Ferrite to Austenite phase.