Numerical experiments for improving the applications of two-phase closed thermosyphons in permafrost regions

Two-phase closed thermosyphons (TPCTs) are widely used in enhancing mechanical strength of foundation soils in permafrost regions. However, engineering problems develop in embankments containing TPCTs. Based on numerical simulations, we herein discuss the influence of four important parameters, namely model size, daily variations in air and ground surface temperatures (AGST), decreasing cooling power of a TPCT, and adiabatic section, on the simulation accuracy or the application results of a TPCT. Results show that the simulated thermal influence of the TPCT can be severely impacted by the model size. It is also found that neglecting daily AGST variations results in 0.3-0.4 degrees C temperature increase in soil 2 m away from the TPCT. The decreasing cooling power of a TPCT can increase the ground temperature. When the cooling power decreases by 30% and 50%, the ground temperature 2 m away from the TPCT increases by 0.2-0.3 degrees C and 0.4-0.6 degrees C in cold seasons, respectively. Although adiabatic section was applied in many TPCTs, but it has limited effect on the cooling performance of a TPCT. The results may help improving the accuracy of a simulation model and help optimize field applications of TPCTs in cold regions.