Performance analysis of LaNi5 added with expanded natural graphite for hydrogen storage system

This paper presents a comparative study of two cases of metal hydride hydrogen storage units working on (i) LaNi5 (ii) Compacts of LaNi5 incorporated with expanded natural graphite (ENG). It has been observed from the previous studies that the hydriding/dehy-driding reactions eventually causes large strain changes, due to which the hydride forming metal alloys disintegrate and form a powder bed. Such reactor beds usually have a low thermal conductivity which minimizes the heat transfer phenomenon occurring during the absorption of hydrogen gas. Therefore, there is a need to implement heat augmenta-tion methods to significantly enhance the thermal conductivity. The objective of this research is to present a 2-D numerical model using Finite Volume Method (FVM) and es-timate the hydrogen storage performance of a cylindrical metal hydride bed for both the cases, i.e. powdered metal hydride bed and ENG compacts-based reactor bed at different values of inlet pressure and heat transfer fluid temperature. In this study, a detailed investigation on the absorption process reveals that reactor beds with compacted disks of LaNi5 and ENG demonstrate an enhanced effective thermal conductivity and efficient mass transfer. The simulation results show that a remarkable improvement in the heat transfer and hydrogen storage capacity with reduced absorption time can be achieved by using LaNi5 and ENG compacts. It was observed that the average reactor bed temperature dropped from 345.13 K to 337.37 K when the ENG based compacted disks was introduced into the reactor bed. Moreover, for supply pressure of 24 bar and fluid temperature of 293 K, the time taken to absorb hydrogen into the rector to achieve stabilized hydrogen storage capacity was estimated to be 446s and 232 s for the case of metal hydride and ENG compacts-based bed, respectively. & COPY; 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study presents a comparative analysis of the performance of metal hydride hydrogen storage units using LaNi5 and compacts of LaNi5 incorporated with expanded natural graphite (ENG). The research highlights the need to enhance thermal conductivity to improve heat transfer during hydrogen absorption. The results demonstrate that the use of LaNi5 and ENG compacts significantly improves heat transfer, hydrogen storage capacity, and reduces absorption time.