The flow characteristics of thermosyphon elevation tube are investigated following the fundamental theory of two-phase flow and solution thermal dynamics. The separated phase flow model for two phases is applied to numerical simulation. The relationships of heat load with amount of elevated solution

amount of vapor

the maximum height of elevated solution

the minimum submersed depth of solution at different cross section and different submersed depth

are plotted to indicate that the elevation effect of the pipes with diameter ratio 19/32 outperforms the others

and the maximum height of elevated solution is higher than 16/32 pipes.The numerical predictions coincide well with the experimental data.