How to calculate Heat loss by radiation in cooling of hot metal by natural air cooling? I want to calculate the heat lost by hot metal put in a mould, to the air. The surface temp of the hot metal drops from 1400 °C to 900°C in this while. There is only natural air cooling in the process. Ambient temperature is 35°C. How should i approach this?To be specific this is the air cooling in the Pig Casting Machine.