Magnetic levitation as a suspension mechanism for cryogenic storage of hydrogen

Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013Current physical supports used in cryogenic storage vessels, in which liquid hydrogen is stored, conduct heat from the environment to the liquid hydrogen which causes the hydrogen temperature to rise and ultimately leads to hydrogen losses due to boil-off. The focus of this study is to investigate magnetic levitation as a possible suspension mechanism, eliminating the use of current physical supports and so doing reducing hydrogen losses due to boil-off. A conceptual design of a container which makes use of magnetic suspension is presented in this study. The concept is validated on the basis of the forces obtainable between a paramagnetic aluminium plate and an electromagnet, as well as the forces obtainable between a neodymium magnet and a bulk Yttrium-Barium-Copper-Oxide superconductor. The forces between the paramagnetic aluminium plate and electromagnet were determined mathematically and tested experimentally. The forces between the magnet and superconductor were determined mathematically and by finite element modelling and simulations using ANSYS Multiphysics. The results obtained in the mathematical- and finite element studies were then validated experimentally. It was found that the forces obtained experimentally between the aluminium plate and electromagnets are inadequate for magnetic suspension of the inner vessel given in the conceptual design. It was also found that the forces obtained experimentally and in the simulation studies for the magnet and superconductor of this study were inadequate due to shortcomings in the magnet and superconductor obtained for experimental tests. The conclusion of this study is that electromagnetic levitation should not be used as a magnetic suspension mechanism for storage of liquid hydrogen. It is also concluded that superconducting levitation can not be used as a suspension mechanism for the concept presented in this study, unless the methods suggested to increase the levitation forces between the neodymium magnet and superconductor are executed.Master