Coiled-tube heat exchanger for High-Pressure Metal Hydride hydrogen storage systems – Part 1. Experimental study

This two-part study explores the development and thermal performance of a coiled-tube heat exchanger for hydrogen fuel cell storage systems utilizing High-Pressure Metal Hydride (HPMH). The primary purpose of this heat exchanger is to tackle the large amounts of heat released from the exothermic hydriding reaction that occurs when the hydrogen is charged into the storage vessel and is absorbed by the HPMH. The performance of heat exchanger was tested using 4 kg of Ti1.1CrMn at pressures up to 280 bar. Tests were performed to assess the influence of different operating conditions on the effectiveness of the heat exchanger at removing the heat in a practical fill time (time required to complete 90% of the hydriding reaction). It is shown that distance of metal hydride particles from the coolant tube has the most dominant influence on hydriding rate, with particles closer to the tube completing their hydriding reaction sooner. Faster fill times were achieved by reducing coolant temperature and to a lesser extent by increasing pressurization rate. By comparing tests with and without coolant flow, it is shown that the heat exchanger reduces fill time by 75% while occupying only 7% of the storage pressure vessel volume. The second part of this study will present a 3D computational heat transfer model of the storage vessel and heat exchanger, and compare the model predictions to the experimental data.