Thermophysical property modeling of a hydrogenic pellet production system

Abstract

Solid hydrogenic pellets are used as fuel for fusion energy machines like the ITER device. This paper discusses the numerical modeling of a Pellet Production System (PPS) that is used to generate these pellets. The PPS utilizes a source of supercritical helium to provide the cooling that is necessary to proceed, liquefy, and solidify hydrogenic material that is ultimately extruded and cut into fuel pellets. The specific components within the PPS include a pre-cooling heat exchanger, a liquefier, and a twin-screw solidifying extruder. This paper presents numerical models of each component. These numerical models are used as design tools to predict the performance of the respective devices. The performance of the PPS is dominated by the heat transfer coefficient and viscous dissipation associated with the solidifying hydrogenic fluid in the twin-screw extruder. This observation motivates experimental efforts aimed at precise measurement of these quantities.