Thermal hazards from a downwards hydrogen impinging jet – Real scale experimental results from up to 700 bar pressure releases in a carpark

Abstract

This study investigates the thermal hazards from the accidental release of hydrogen through a nozzle in a mechanically ventilated confined compartment, simulating the flow through a thermally activated pressure release device (TPRD) from a hydrogen vehicle into a car park.

The experimental work was conducted on a real scale, with hydrogen released through 0.5 mm and 1.0 mm diameter nozzles from a tank at storage pressures of 350 bar and 700 bar. The thermal effects of an impinging hydrogen jet fire released at different angles from the TPRD exhaust pipe were analyzed.

A detailed analysis correlating the thermal effects with TPRD size, storage pressure, and ventilation rate is presented. Results indicate that reducing the TPRD diameter to 0.5 mm decreases the maximum temperature behind the car from 500 °C to 250 °C at the same storage pressure, reducing harm distance but increasing exposure time to high temperatures. Temperature results in the ventilation pipe from all experiments remained below the 300 °C specified in regulations. Temperature profiles around the car model can be used for first responder strategies. Our findings provide valuable empirical data from real-scale experiments for the safety assessment of hydrogen-fuelled vehicles and contribute to the development of guidelines for managing thermal hazards in confined spaces.