Performance analyses of two-phase closed thermosyphons for road embankments in the high-latitude permafrost regions

Two-phase closed thermosyphons (TPCTs) are widely used in infrastructure constructions in permafrost regions. Due to different climatic conditions, the effectiveness of TPCT will also be different, especially in the extremely cold region of the Da Xing'anling Mountains. In this study, a series of three-dimensional finite element TPCT embankment models were established based on the Zhangling-Mohe highway TPCT test section in Da Xing'anling Mountains, and the thermal characteristics and the cooling effect of the TPCTs were analyzed. The results indicated that the TPCTs installed in the northeastern high-latitude regions is effective in cooling and stabilizing the embankment. The working cycle of the TPCTs is nearly 7 months, and the cooling range of the TPCTs can reach 3 m in this region. However, due to the extremely low temperature, the TPCT generates a large radial gradient in the permafrost layer. Meanwhile, by changing the climate conditions, the same type of TPCT embankment located in the Da Xing'anling Mountains, the Xiao Xing'anling Mountains, and the Qinghai-Tibet Plateau permafrost regions were simulated. Based on the comparison of the climate differences between the Qinghai-Tibet Plateau and Northeast China, the differences in the effectiveness of TPCTs were studied. Finally, the limitations of using existing TPCTs in high-latitude permafrost regions of China were discussed and the potential improvements of the TPCT in cold regions were presented.