Abstract: The energy-saving mechanism of blackbody directional radiation technology was investigated. Based on a chamber heating furnace with an intermediate radiator in a steel plant， a physical model with intermediate radiators was established. A transient 3-D mathematical combustion model coupled with heat transfer and fluid flow in the furnace was developed based on the CFD commercial software Fluent to simulate the combustion and temperature distribution in the furnace. The model was verified according to experimental results. The research results show that the installation of the intermediate radiators changes the flow pattern in the combustion chamber of the furnace and the view factor of the furnace wall to the slab for solid radiation， and enhances the radiant heat transfer intensity of the slab surface for both gas radiation and solid radiation. The combustion temperature is reduced by about 20K， the slab heating speed is increased by 16.7%， and the highest temperature of the slab surface is increased by 40K. The improvement of heating efficiency brings a better energy-saving effect.

Key words: heating furnace; directional radiation; numerical simulation; multi-physics field; energy-saving