Loading procedure for testing the cryogenic performance of cryo-compressed vessel for fuel cell vehicles

Abstract

To overcome the disadvantages of high cost and hazards in the cryo-compressed vessel test with liquid hydrogen, a combined process with liquid nitrogen and compressed helium was carried out. A computational fluid dynamics (CFD) model was introduced to simulate the loading procedures required to generate suitable conditions in a cryo-compressed vessel with a Carbon Fiber wrapped Aluminum liner. Element-based finite volume method (FVM) and a k – ω based shear stress transport (SST) model have been used to simulate the thermal flow of helium. The simulation model was validated by a similar experiment result and the data from the U.S. National Institute of Standards and Technology reference database. To investigate the thermal characteristics of the vessel, temperature distribution, loading performance, and helium consumption were analyzed at various filling mass flow rates. The simulation results confirmed that cryo-compressed test conditions could be achieved by liquid nitrogen precooling followed by pressurization with compressed helium. The cryogenic conditions were highly depended on the inlet mass flow rate and the corresponding loading time. Lower inlet mass flow rates (longer loading times) leaded to a high temperature increase of 84.04 K in Carbon Fiber during the loading, which was minimized to only 1.65 K when using the highest mass flow rate. Considering both final condition and loading efficiency, high filling speed is optimal for single tests, while lower filling speeds were more appropriate for cyclic fatigue testing of vessels because of lower helium consumption and equipment costs. Not only thermal fluid was simulated to investigate the loading parameters to generate cryo-compressed conditions, but also the thermal transfer result of composite materials. Our findings are expected to assist in the design and operation of this challenging experiment in a safe and efficient way.