Research On Heat Transfer Model Of Capillary Front End Heat Exchanger Of Metro Source Heat Pump And Synergy Characteristics Of System Thermal Process

With the rapid development of underground transportation system,the problems of high energy consumption and thermal accumulation in tunnels are gradually highlighted.In response to the above problems,scholars in China and abroad have been more inclined to use the heat in tunnel only on the basis of solving thermal accumulation in the past,so as to reduce energy consumption when solving the deterioration of the thermal environment in tunnel.As one of the more effective ways,the heat pump system with capillary front-end heat exchanger in tunnel lining is increasingly favored by scholars.In this paper,according to a demonstration project,the physical model of Capillary front heat exchanger(Capillary front Heat Exchanger)is determined,and then it is reasonably simplified.The CHE flow-thermal coupling heat transfer model in circular composite medium based on the assumption of surface heat source is established.The solution of the coupling heat transfer model is obtained by combining theory with numerical method.In order to improve the source side components of subway source heat pump system,the heat source part in tunnel is calculated,and the prediction model of air temperature in the tunnel is obtained.Based on the coupled heat transfer model of heat exchanger and the tunnel air temperature prediction model,the corresponding numerical simulation module is built in TRNSYS platform.The CHE heat transfer performance test data and the measured air temperature in tunnel are used to verify the simulation modules above.The results show that the two simulation modules are reliable and the accuracy meets the engineering requirements.The performance tests were carried out for the edited CHE flow-thermal coupling heat transfer model simulation module and the air temperature prediction model simulation module in tunnel.The effects of flow velocity in the tube,the supplying water temperature and the rock mass type on the heat transfer of CHE and the effects of tunnel 0depth,train speed and train departure logarithm per hour on the air temperature change in the tunnel were tested.It provides a theoretical basis for CHE designing.Combine the edited simulation module above with the existing modules in TRNSYS to build a front-end heat exchanger subsystem model and a subway source heat pump system simulation model.The operating conditions of the front-end heat exchanger and the operating conditions of the subway source heat pump system in a typical year were simulated respectively,and the operating parameters were analyzed.The simulation results show that the thermal response of outdoor air temperature,building load,CHE heat flux density,air temperature in the tunnel,and surrounding rock temperature on the tunnel surface are not synchronized;the amplitude range of each temperature is also different.After studying and analyzing the cooperative mechanism of the source-system-end of the system,it is believed that the operation strategy of the heat pump unit can be optimized by this,reducing the initial investment and operating cost of the heat pump system,and saving energy and reducing losses.It provides a theoretical basis for the optimal design and energy-saving operation of the subway source heat pump system.