Numercial analysis on the thermal performance of capillary heat exchange system in metro running tunnel

During the operation of the capillary heat exchange system in the metro tunnel,the pipe length,pipe spacing and air velocity have different effects on the heat transfer effect and show certain rules.Taking Kunming as an example,a single-factor analysis method was used to establish multiple-capillary model,and the variation of different influencing factors in the heat transfer process was obtained.On this basis,a single-capillary model was established to analyze the thermal interference variation of the pipe spacing between the two models.Under the condition of ensuring the capillary outlet water temperature and heat flux,the relevant parameters of the capillary heat exchanger were optimized.The results show that the pipe length of the capillary heat exchanger should be kept within 3-5 m,the pipe spacing is maintained at 20-30 mm,and the capillary heat exchanger of each set can be operated in parallel to ensure that heat exchanger have better heat transfer performance.During the system stop running,the air velocity in winter and summer has different effects on the recovery of surrounding rock.