多年冻土区天然地面耦合热管的数值传热分析及优化

为了青藏铁路多年冻土路基耦合热管优化设计的需要,建立多年冻土区天然地面耦合热管的相变传热模型,利用该模型研究不同热管管径、气候条件和冷凝段与蒸发段长度比对热管传冷量的影响。结果表明:大管径的热管对于提高热管的传冷量是有利的;在冷凝段与蒸发段长度比大于0.9的条件下,热管传冷量随长度比增大得并不明显,因此建议优化的冷凝段与蒸发段长度比取为稍大于0.9的值;与年平均气温较高的多年冻土区相比,年平均气温较低的多年冻土区更有利于热管的传冷。对比模型计算值和现场实验值表明,提出的模型与实际拟合良好。

Numerical Heat Transfer Analysis and Optimization for Thermosyphons Coupled with Natural Ground in Permafrost Regions

In order to satisfy the needs of the optimization design for thermosyphons coupled with embankment in permafrost regions in Qinghai--Tibet railway, the heat transfer model with phase change for thermosyphons coupled with natural ground in permafrost regions is established. According to this model, the influences of different diameters of thermosyphons, climatic conditions and the length ratio of condensation section to evaporation section on heat transfer rate are investigated. The results indicate that the larger diameter of thermosyphon is the better to the enhancement of heat transfer rate. The increase of heat transfer rate with the increase of length ratio is not obvious when the length ratio of condensation section to evaporation section is larger than 0. 9. Consequently, the optimum length ratio of a little larger than 0. 9 is suggested. In comparison with permafrost regions with higher annual mean temperature, permafrost regions with lower annual mean temperature is more beneficial to the enhancement of heat transfer rate. Moreover, the comparisons between the simulated values and the field data indicate that the established model agrees well with the practice.