In this study, the fluidized bed heat transfer technology is introduced into two-phase closed thermosyphon (TPCT) to build a novel thermosyphon system, which aims to improve the heat transfer performance of TPCT. A series of experiments are conducted to investigate the joint effects of particle size, amount of added particles and heating power on heat transfer characteristics of the novel thermosyphon. Results show that the heat transfer performance of TPCT is significantly improved in the evaporator section because of the addition of silicon carbide particles. However, in the condenser section, the existence of particles leads to the deterioration of heat transfer. In general, the heat transfer enhancement effect of the large size particles is superior to that of the small size particles. The overall thermal resistance is reduced because of the addition of large size particles. The 3D diagrams are established to assess the joint effects of various parameters. (c) 2021 Elsevier B.V. All rights reserved. In this study, the fluidized bed heat transfer technology is introduced into two-phase closed thermosyphon (TPCT) to build a novel thermosyphon system, which aims to improve the heat transfer performance of TPCT. A series of experiments are conducted to investigate the joint effects of particle size, amount of added particles and heating power on heat transfer characteristics of the novel thermosyphon. Results show that the heat transfer performance of TPCT is significantly improved in the evaporator section because of the addition of silicon carbide particles. However, in the condenser section, the existence of particles leads to the deterioration of heat transfer. In general, the heat transfer enhancement effect of the large size particles is superior to that of the small size particles. The overall thermal resistance is reduced because of the addition of large size particles. The 3D diagrams are established to assess the joint effects of various parameters.