Effective thermal conductivity model applied in pellet bed reactors for nuclear thermal propulsion
Nuclear thermal propulsion(NTP)is a new-type nuclear reactor application which chooses hydrogen gas as the working medium,heated by fuel pellets in the reactor core to extremely high temperature,so as to achieve huge thrust and high specific impulse.Based on the typical design of reactor core in American NTP rocket engine programs,the effective thermal conductivity model of high temperature gas-cooled reactors was used and preliminary applied,for the analysis of the pellet bed mixed with smaller fuel particles and higher temperature hydrogen gas.The influences of fuel type,pellet diameter and pellet bed porosity on the thermal conductivity of the reactor core were also obtained in this paper.Meanwhile,considering that the fuel pellet was usually coated by multi-layers with different materials,the homogenization method was used for equivalent calculation in thermal properties of these materials,aimed to provide the average thermal conductivity parameters of solid domain for the effective thermal conductivity model.According to the calculation results,the pellet diameter and pellet bed porosity have a greater impact on the effective thermal conductivity,relative to the components thermal conductivity,especially under high temperature conditions that the radiation heat transfer is dominant.
effective thermal conductivitymodel applicationpellet bed reactorsnuclear thermal pro-pulsion