Observation Study on the Cooling Radius of a New Type of Heat Pipe in the Middle-Latitude Swampy Permafrost Regions

The Chaidaer-Muli Railway (abb., Chaimu Railway) was constructed in the Qilian Mountains, where middle-latitude swampy permafrost regions are developed. About 20km embankment was equipped with heat pipes. Taking into account the characteristics of local climate, the interaction between heat pipe and ground soils and secondary standard adopted by the Chaimu railway in accordance with the national railway, the structure and design parameter of the heat pipe were optimized. The wick structure and the adiabatic section were removed; the condensing section was reduced to 1.5m in length. In order to examine the cooling effect of heat pipe in the middle-latitude swampy permafrost, a testing field was built up in the middle part of the Chaimu Railway in the year of 2008. According to the field data from 2008 to 2010, cooling radius of heat pipe is 2.4m if it is treated as a standard that mean annual ground temperature at 3.0m deep was cooled down by -0.5°C. The results proved that design interval between heat pipes can meet the demands of cooling frozen soil roadbed in the Chaimu Railway.