Heat Extraction by Packed Beds Constrained by Neutron Shielding Requirements and Radio Frequency Plasma Heating: An Application to Aneutronic Fusion Reactors

Abstract

The Princeton Field-Reversed Configuration (PFRC) Micro-reactor presents unique neutron shielding and fusion energy capture requirements due to its compact nature. Efficient thermal energy capture and extraction is critical to the implementation of the PFRC. The goal of this project is to design and implement an experimental setup to measure the temperature profile under heating and cooling conditions within a packed pellet bed. This was done by constructing a test set up scaled by pellet diameter with wall heating on one side. Carbon steel pellets of two varying sizes were selected, 3 mm and 7 mm. Each system was heated to steady state and then cooled with a working fluid of compressed air. The energy absorption of the pellet bed during heating developed a deeper understanding for the relationship between bed size and energy capacity. Energy extraction due to air showed the importance a hot outlet flow temperature will play in creating an efficient heat exchanger. The conductivity of the pellet bed will need to be high enough such that a temperature gradient along the direction of wall heating can facilitate heating of the entire incoming flow. This was seen to relate heavily to the void fraction of the respective beds such that as the voidage increases so does conduction within the bed.