Evolution of temperature fields and heat transfer mechanisms in concrete structures subjected to hydrogen jet flame impingement

To clarify the temperature field evolution and heat transfer mechanisms of concrete structures under hydrogen jet flames, a self-developed hydrogen gas jet flame exposure platform has been established. C30 concrete specimens were tested under hydrogen mass flow rates of 0.025, 0.0375, and 0.05 g/s and exposure durations of 30 and 60 min. Infrared thermography and embedded thermocouples were used for synchronous temperature measurement. The results showed that the peak surface temperature reached 912.8°C, and the internal temperature followed a three-stage evolution of rapid rise, 100°C stagnation plateau, and slow rise. Under 0.05 g/s-60 min condition, the 500°C and 300°C isotherms reached depths of 25 and nearly 50 mm, respectively. The penetration depth of the critical temperature front as determined through experiments provides a quantitative reference for local thermal protection of concrete components exposed to hydrogen gas jet fires, as well as for post fire detection.