Session: 10-05-01: Multiphase Flows

Paper Number: 95762

95762 - Analysis and Management of Thermal Energy Release During Quench in a Superconducting Magnet 

In low temperature superconducting (LTS) magnets built using (cryogenic) forced flow cooled superconductors, such as those designed for particle accelerators and thermonuclear fusion reactors, the operating stability and quench (sudden transition from superconducting to normal state) is a complex phenomenon. Designing a safety system to prevent over-pressurization of the cryogenic containment vessel from the dissipation of the stored magnetic energy requires accurate analysis of the stability and quench characteristics. In most cases, the quenched LTS magnet is isolated from the rest of the cryogenic system, and the cryogen (helium) is expelled from the LTS magnet cryostat via a pressure relief valve (PRV) to prevent over-pressurization. This loss of cryogenic coolant (release to atmosphere), as well as the stored refrigeration results in increased operational cost (to replenish the helium), and recovery time for the LTS magnet to be operational following a quench. A novel concept for energy and cryogenic inventory management during a LTS magnet quench has been proposed and demonstrated. The concept for energy and cryogenic inventory management (and recovery) considers a cryogenic buffer volume to absorb both the mass and energy released during the quench of a LTS magnet. A one-dimensional transient fluid network model with conjugate heat transfer from the composite superconducting magnet coil is developed using the FLOWER code. Empirical correlations for boiling heat transfer in liquid helium are used in this model. The developed fluid network model is used to predict the boil-off flow generated during the quench in a superconducting magnet. To contain this boil-off flow within the cryogenic system, it can be directly injected into a pool of saturated liquid helium stored in a cryogenic buffer volume. The resulting direct contact heat exchange between the liquid helium and the quench release flow cools the latter at the expense of generating more boil-off helium and hence pressurizes the buffer vessel. Adequate knowledge on several thermo-physical and transport characteristics pertaining to this proposed process is required for accurate estimation and proper sizing of the quench energy and cryogenic inventory management system. The development of a semi-analytical heat transfer model to simulate the direct contact heat exchange for this application is also discussed. It includes the effect of sensible and latent heat contributions, liquid surface tension, and the vertical motion of the injected bubble flow on the convection and on the saturation conditions of the vapor at real operating conditions. The developed numerical models combined together can be used as a simplified but accurate design tool for the sizing and process estimation for such a system.

Presenting Author: Nusair Hasan Michigan State University

Presenting Author Biography: Dr. Nusair Hasan is a Cryogenics Staff Engineer at the Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU). He is responsible for the process and mechanical design of large-scale 2 Kelvin and 4 Kelvin helium refrigeration systems, cryostats, and cryogenic fluid transfer systems used at FRIB, as well as to carry-out research and development activities in the advancement of cryogenic processes and technology, specifically in regards to cryogenic helium refrigeration and critical supporting sub-systems. His major research interests are in process optimization of thermal (cryogenic) systems, cryogenic heat exchangers, multi-phase flow and heat transfer, and gas purification. Dr. Hasan graduated from Drexel University with a Ph.D. in Mechanical Engineering. He worked at the Thomas Jefferson National Accelerator Facility for three and half years as a cryogenics process engineer, where he was responsible for process design and operation of the facility’s several cryogenic systems and sub-systems. Dr. Hasan has over ten years of experience in teaching and research relating to thermal systems and cryogenics, working at various institutions including Drexel University and at Bangladesh University of Engineering and Technology.

Authors:

Nusair Hasan Michigan State University
Venkatarao Ganni Michigan State University / Facility for Rare Isotope Beams
Peter Knudsen Michigan State University / Facility for Rare Isotope Beams