The effect of evaporation section setting on the thermal performance of a closed thermosyphon combined with the fluidized bed heat transfer technology is experimentally investigated by varying the solid holdup (10-20%) and input power (50-300 W). Pure water and glass beads are chosen as the working media in a smooth copper tube. The results show that the particle addition may enhance the heat transfer of the thermosyphons under different evaporation section settings. The maximum reduction rate of the overall thermal resistance is 23.5% with a evaporation section length of 200 mm at solid holdup of 15% and input power of 300 W. The overall thermal resistances of the two-phase and three-phase thermosyphons decrease with the increase in evaporation section length. The upward movement of the evaporation section is beneficial to the heat transfer of the two-phase closed thermosyphon, but is not conducive to that of the three-phase closed thermosyphon. (C) 2020 Elsevier B.V. All rights reserved.