Experimental data- hydrogen safety, thermal effects

The study of hydrogen releases from high-pressure storage systems is important for practical applications for 1) hydrogen driving vehicles: technology and safety, and 2) validation of computational fluid dynamic models. The focus of this paper is on accidental releases that occur due to for example a failure of the TPRD (thermal pressure-activated relief device) with immediate ignition. The physics and dynamics of such releases have to be understood and the importance of the resulted effects needs to be implemented into the development of RCS (regulations, codes, and standards) and mitigation systems. In this paper the real scale experimental results are presented. Releases from the hydrogen tank with storage pressure 350 and 700 bar through 0.5 mm and 1.0 mm diameter into a container with an installed forced ventilation system are presented. The thermal effects resulting from a different angle of the TPRD exhaust pipe were tested. The resulting hydrogen jet fires showed direct dependence on the mass flow rates. Higher mass flow rates resulted from the bigger TPRD diameter or higher storage pressure caused higher temperatures in the ventilation pipe and in the container. A more detailed analysis of the thermal consequences related to TPRD size, storage pressure, and ventilation rate is presented. Results from all the experiments showed temperatures below specified in the regulations, 300 °C, in the ventilation pipe. Low temperatures measured at the front of the car and high temperatures behind will be used for the mitigation strategies and first response guidance. Generally decreasing TPRD diameter to 0.5 mm decreased max temperature behind the car from 500 °C to 250 °C from the same storage pressure, and decreasing harm distance.