Multi-field coupled modeling of metal hydride hydrogen storage: A resistance atlas for H2 absorption reaction and heat-mass transport

Abstract

Metal hydride hydrogen storage (MHHS) is an efficient technology to raise the hydrogen storage level. Currently, insight into the interaction between reaction and heat-mass transfer to achieve excellent storage performance is still a pressing issue. Therefore, in a specific example of LaNi5, this work adopted a transient multi-field coupling model for the hydrogen storage reactor to investigate the reaction-transport resistance characteristics, as well as the reaction heat management and enhancement strategy. According to the investigation, the operating parameters (such as temperature, pressure and porosity) have significant influences on the absorption reaction evolution. When the temperature increases from 55 °C to 65 °C, the saturated hydrogen absorption capacity decreases from 5.28 to 1.76. When the pressure decreases from 1.6 MPa to 0.4 MPa, the reaction evolution time will increase from 42.8 min to 121.6 min, the growth rate was 64.8%. Large porosity also contributes to reaction rate and reduces the average temperature of the reaction bed (RB). With external cooling measures, the absorption evolution can be significantly boosted. In addition, a general resistance atlas capable of clarifying the reaction and heat-mass transport characteristic is drawn. According to the characters of reaction resistance Rr, heat resistance Rh (including conduction R(lλ) and convection R(1h)) and flow resistance (Rf), the hydrogen absorption evolution is distinctly divided into four zones, among which the Rh dominating zones is the most remarkable that means the heat management and heat transfer enhancement still retain lots of margin for raising the H2 absorption evolution. The performance tuning limit is also presented in the atlas. Currently, focusing on internal-conduction and external-convection enhancement for the reactor design is quite effective and efficient in improving MHHS performance.