Effect of precooled inlet gas temperature and mass flow rate on final state of charge during hydrogen vehicle refueling

Short refueling time and high final state of charge are among the main hydrogen car user's requirements. To meet these requirements, without exceeding the tank materials safety limits, hydrogen precooling is needed. Filling experiments with different inlet gas temperatures and mass flow rates have been executed using two different types of on-board tanks (type 3 and 4). State of charge has a strong dependency on the inlet gas temperature. This dependency is more visible for type 4 tanks. Lowest precooling temperature (−40 °C) is not always required in order to meet user's requirements, so energy savings can be achieved if the initial conditions of the tank are correctly identified. The results of the experiments performed have been compared with the SAE J2601 look-up tables for non-communication fillings. A big safety margin has been observed in these tables. Refueling could be performed faster and with less demanding precooling requirements if the initial conditions and the configuration of the hydrogen storage system are well known.