Three-dimensional simulation of the effective thermal conductivity of tungsten fuzz by the lattice Boltzmann method

Abstract Tungsten (W) fuzz formed on divertor targets under helium plasma irradiation significantly alters the thermal conduction properties of the underlying W substrate. Hence, it is essential to conduct detailed studies on its thermal conductivity. Modeling heat transfer in the media characterized by complex rough morphology and porous structure is a formidable challenge. To address this, a novel computational framework named Lattice Boltzmann Simulation (LBS), leveraging the lattice Boltzmann method (LBM), has been developed to simulate three-dimensional heat conduction within W fuzz and calculate its effective thermal conductivity (ETC). The modeled ETCs of fuzzy layers with different thicknesses by LBS code show a good agreement with the experimental values measured in the NAGDIS-II device. Furthermore, an empirical fitting formula that describes the temperature-dependent ETC of W fuzz can be derived based on the LBS simulations, enabling rapid thermal conductivity calculations. Leveraging this relationship, a 1D heat transfer model has been utilized to investigate the impacts of W fuzz on thermal conduction for divertor targets with fuzzy surfaces. The results reveal that the formation of W fuzz reduces the critical heat flux required for surface melting, thereby exacerbating the risk of material damage under high heat loads.