Term of Award

Summer 2024

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Mechanical Engineering

Committee Chair

Hayri Sezer

Committee Member 1

Hossain Ahmed

Committee Member 2

David Calamas

Committee Member 3

Jerry Hunter Mason

Committee Member 3 Email

jerry.mason5031@gmail.com

Abstract

As a promising clean energy carrier hydrogen has recently gained significant interest, but its efficient and safe storage is a major challenge. Compared to the gaseous state and liquid state, metal hydrides (MH) offer a potentially more effective storage approach for hydrogen. However, the main challenge in this approach is the low thermal conductivity of the MH bed that leads to low heat transfer and ultimately to higher charging and discharging times. The purpose of this work is to develop an in-house comprehensive heat and mass transfer model for hydrogen sorption in MH reactors to simulate the dynamic behavior of hydrogen storage. A 2D axis-symmetrical mathematical model for hydrogen absorption and desorption is presented for a cylindrical LaNi5 reactor. The model is validated using experimental temperature and reaction kinetics data while the relation for the equilibrium pressure is derived from PCT parameters, plateau flatness, and hysteresis factors making it a function of both temperature and hydrogen to metal atomic ratio [H/M]. A comparative examination of two models, one incorporating Darcy's velocity due to pressure gradients and the other neglecting it, demonstrates that while Darcy's law introduces numerical instability in the model, its overall effect on model outcomes can be neglected for the analyzed reactors. The developed model is then used to conduct different parametric studies to investigate the effect of discharging pressure, heating fluid temperature, porosity, and reactor size on the time histories of temperature and reacted fraction profiles. The effect of changing the non-homogeneous Neumann to Dirichlet boundary condition is also demonstrated to anticipate the utilization of phase change materials (PCM) instead of the cooling fluid. The research findings reveal the influence of charging/discharging pressure on the maximum/minimum temperatures attained and reaction kinetics, while highlighting the predominant impact of fluid temperature on sorption kinetics. The model can be conveniently adapted for other metal hydrides and system configurations, including MH reactors with heat transfer fluid or finned heat exchangers or both. This work contributes to the development of more efficient hydrogen storage technologies, bringing us closer to realizing the potential of hydrogen as a clean and sustainable energy carrier.

Research Data and Supplementary Material

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