Understanding thermal transfer mechanisms in BOF converter is a key for higher energy efficiency, involving higher production capacity and lower CO2 emissions through low hot metal ratio capability. The developed model achieves a coupled description of the major phenomena: refining reactions, mass transfers between phases, scrap melting, post-combustion, slag formation. The calculated exhaust fumes enthalpy is fitting well the measured thermal balance trials with industrial converter when implementing a detailed description of the post-combustion. This model, compatible with real-time use, is also a valuable tool for further improvement in dynamic control of the process.