Researchers improve hydrogen absorption in metal hydrides using semi-cylindrical coil heat exchanger
Researchers from the University of Technology Sydney (UTS) and Queensland University of Technology (QUT) have developed a new method to improve hydrogen absorption in metal hydrides. An open-access paper on their approach is published in Scientific Reports.
Metal hydrides (MH) are known as one of the most suitable material groups for hydrogen energy storage because of their large hydrogen storage capacity, low operating pressure, and high safety. However, their slow hydrogen absorption kinetics significantly decreases storage performance. Faster heat removal from MH storage can play an essential role to enhance its hydrogen absorption rate, resulting in better storage performance.
In this regard, the present study aims to improve heat transfer performance to positively impact the hydrogen absorption rate of MH storage systems. A novel semi-cylindrical coil is first designed and optimized for hydrogen storage and embedded as an internal heat exchanger with air as the heat transfer fluid (HTF).
… Results from this study demonstrate that MH storage performance is significantly improved by using a semi-cylindrical coil heat exchanger (SCHE). The hydrogen absorption duration reduces by 59% compared to a normal helical coil heat exchanger. The lowest coil pitch from SCHE leads to a 61% reduction of the absorption time. In terms of operating parameters for the MH storage with SCHE, all selected parameters provide a major improvement in the hydrogen absorption process, especially the inlet temperature of the HTF.—Larpruenrudee et al.
A problem with metal hydride for hydrogen energy storage has been its low thermal conductivity, which leads to slow charging and discharging times. First author Puchanee Larpruenrudee, a PhD candidate in the UTS School of Mechanical and Mechatronic Engineering, said faster heat removal results in faster charging times.
Several internal heat exchangers have been designed for use with metal hydride hydrogen storage. These include straight tubes, helical coil or spiral tubes, U-shape tubes, and fins. Using a helical coil significantly improves heat and mass transfer inside the storage. This is due to the secondary circulation and having more surface area for heat removal from the metal hydride powder to the cooling fluid. Our study further developed a helical coil to increase heat transfer performance.—Puchanee Larpruenrudee
The researchers developed a semi-cylindrical coil as an internal heat exchanger, which significantly improved heat transfer performance. The hydrogen charging time was reduced by 59% when using the new semi-cylindrical coil compared to a traditional helical coil heat exchanger.
Characteristics of selected geometries for metal hydride reactors. (a) With helical tube heat exchanger, and (b) with semi-cylindrical tube heat exchanger. Larpruenrudee et al.
They are now working on the numerical simulation of the hydrogen desorption process, and continuing to improve absorption times. The semi-cylindrical coil heat exchanger will be further developed for this purpose.
The researchers aim to develop a new design for hydrogen energy storage, which will combine other types of heat exchangers. They hope to also work with industry partners to investigate real tank performance based on the new heat exchanger.
Larpruenrudee, P., Bennett, N.S., Gu, Y. et al. (2022) “Design optimization of a magnesium-based metal hydride hydrogen energy storage system.” Sci Rep 12, 13436 doi: 10.1038/s41598-022-17120-3