Liquid Lithium Delivery to Capillary Porous Systems for Fusion Experiments

Abstract

This paper details the steps taken and the results achieved in a Senior Thesis Project aimed at designing and testing a System for Liquid Lithium Delivery to a Capillary Porous System (CPS) for use in Fusion Experiments at the Princeton Plasma Physics Lab (PPPL). The project is a year-long project conducted by Jens Clausen with the help of Professor Robert Goldston. A significant portion of the project is spent understanding and simulating the flow of liquid through a CPS. The paper begins by examining the theoretical flow through a circular, disc-shaped CPS. Equations are derived for the time taken for the liquid front to penetrate to a given radius. The upper limit of this penetration is examined through the Lucas-Washburn Equation before discussing the effects of evaporation of the liquid on the liquid front’s position; The concept of Dry-Out is introduced and used to describe the flow’s behaviour under evaporation. Equations for the power required for Dry-Out are derived. Simulations are conducted to find the pressure distribution in the CPS disc. The results of these simulations are compared with theoretical results produced by a paper on Evaporation Limited Radial Capillary Penetration in Porous Media by Mingchao Liu and are found to be consistent. Further simulations are conducted to examine the effect of geometry on CPS Dry-Out. For each simulation, a required power is calculated and a mass flow rate through evaporation is determined. Tests are conducted on the CPS discs to collect data for the time taken for different liquids to penetrate across the entire length of the discs. The data collected is used to inform later decisions in the design process and build understanding of the physics involved. A preliminary design for a test system, which works with water, is presented with accompanying drawings of the design produced in CREO. The test system is designed for use in a work-from-home environment which allows for use regardless of COVID-19 related restrictions. A system utilizing a feedback loop for autonomous control of the power supplied to the system is presented. This system allows the user to impose and control the level of Dry-Out on the CPS. Finally, future developments that would be needed to better understand and build a system for Fusion Experiments are presented along with the challenges they bring.