Study On Heat Transfer Characteristics Of Heat Exchanger In Capillary Heat Pump System Of Subway Tunnel

The surrounding structure of subway tunnels and surrounding rock and soil is a great heat capacity,which is rich in renewable energy and can be used for heating and cooling.The traditional subway environmental control system is independent of the buried ground source heat pump system,which makes the utilization of urban shallow geothermal energy more restricted.In this project,the capillary network heat exchanger is embedded between the waterproof layer and the second lining of the subway tunnel to form an embedded capillary heat exchanger and heat exchange with the underground rock and soil,so that the metro ring system and the buried ground source heat pump system are organically combined,In order to achieve the subway platform for the summer cooling in winter for the ground floor heating.The main contents of this thesis are as follows: Firstly,the factors that influence the heat transfer process of embedded capillary heat exchanger are analyzed,and the coupling heat transfer between capillary network,surrounding rock and air is considered.Based on the energy equation,According to the heat transfer theory of the composite medium,using the separation variable method and Green's model,the heat transfer model of the capillary heat exchanger is designed and simplified.Function method to obtain the theoretical solution of embedded capillary heat exchanger.Thirdly,considering the thermal disturbance in the thermal environment of the tunnel,the air temperature and the heat dissipation of the train running in the tunnel are taken into account,and the thermal disturbance model is established.After the whole year operation of the embedded capillary heat exchanger,Temperature field;Fourthly,through the thermal response test of the capillary network heat exchanger and the surrounding surrounding rock,the influence of the flow rate and the inlet temperature of the capillary network heat exchanger tube on the heat transfer is studied.And then use the method of numerical simulation to compare the calculated value and the experimental data with the experimental data to prove the rationality of the model.Finally,the experimental value and the theoretical calculation value were compared and analyzed to verify the reliability of the solution;The fuzzy optimization theory is applied to the optimal design of the capillary heat exchanger,which solves the problem that the target is too much to consider in the design process.In this project,field test is carried out to establish the thermal disturbance model in the tunnel.Considering the coupling relationship between the capillary network and the air in the tunnel,the temporal and spatial distribution of the temperature field in the surrounding rock is studied.Based on the fuzzy optimization theory,a simplified mathematical model of the capillary heat exchanger was established by using the multi-objective fuzzy optimization method,and the multi-objective was solved by the linear weighting method.It provides a theoretical basis for the application and popularization of embedded capillary heat exchanger in subway tunnel engineering.