Analysis For Heat Transfer And Multi-Field Coupling Of Energy Geostructures

The energy geostructure,which combines the ground source heat pump and the building structural components,is one of the new energy saving and environmentfriendly technologies and can effectively utilize the shallow geothermal energy,bringing obvious environmental and economic benefits.With the rapid development of the ground source heat pump technology and economic state in China,the demand for a better environment and ecology is increasing,and the energy geostructure has become a new and environmentally friendly new energy technology worthy of popularization and application.The main purpose of this paper is to design and analyze the heat exchanger of the energy geostructures and to make a preliminary design of the Ground Heat Exchanger(GHE)by using the classical analytic method as well as the COMSOL Multiphysics.By deriving the analytical solution of dynamic heat load in Line Source problems,the application range of the classical analytic method is extended;the analysis ability of the Finite-Element(FE)software is tested by comparing test data and the outcome of FE analysis;the feasibility of energy tunnels is discussed in the case of a real project.The main achievements of this paper are as follows:1.The classical heat transfer theory of the GHE is used to derive the analytical solution of Finite Line Source(FLS)and Infinite Line Source(ILS)models under dynamic loads and is compared with the ANSYS finite element software.The experimental results show that the analytical solution derived can effectively calculate the long-term working condition of the heat exchanger under a variable heat flux,and can also be combined with the Moving Line Heat Source(MLS)theory to calculate the analytical solution of variable heat flux under considerable groundwater seepage.2.The Scaling Laws for the thermo-hydraulic coupling(TH coupling)problem in the saturated soil in centrifuge tests is completely derived,and the heat transfer in the Savvidou centrifuge test,1988,simulated using COMSOL.The importance of centrifuge test in the scaled model analyses is explained;when dimensions and parameters are scaled according to the Scaling Laws,it is believed,the model can correctly reflect the heat transfer mechanism in the prototype,and important variables such as temperature and velocity in TH coupling cases for model and prototype equal each other.3.On the basis of Xining-Chengdu High-Speed Railway super-long tunnel project constructed in the cold climate of Xining,the FE model of the GSHP in energy tunnels is established by using the COMSOL Finite-Element software.The meteorological data of Xining and the heating load are calculated,and the GSHP system of the invert heat exchanger energy tunnel is designed and analyzed.Sensitivity analyses of important parameters such as seepage velocity are carried out.The study shows that the tunnel can be heated effectively by using GSHP systems,and energy tunnel would have a prospective future in avoiding freezing and protecting the internal structures of tunnels in freezing conditions.