Numerical Simulation Of Underground Heat Exchangers Under Coupled Heat Conduction And Groundwater Advection Conditions

Ground source heat pump(GSHP) system is one of the most promising innovative air-conditioning technology aimde at energy conservation and environment protection,and is one of the most advanced topics in international HVAC industry. This technology has already head for mature abroad, but still be placed in a research stage in the domestic. Various works just and gradually launch and lay good foundation for the engineering application which strongly expands ground source heat pump.The underground geothermal heat exchanger(GHE) always is GSHP technology's research key, but the physical phenomenon inside the soil is complicated, and groundwater advection is widespread and existent. The GHE's heat transfer capability is influenced by groundwater advection,and heat conduction and groundwater heat advection is coupled. Based on porous medium theory, the GHE's mathematical model under coupled heat conduction and advection is established with correspond simplifications. Through numerical simulation,the performance of the GHE with groundwater advection is analyzed. Furthermore, the heat transfer effect of the GHE and the soil temperature field under groundwater advection is influenced by three parameters such as the rate of fluid flow,the soil permeability and the soil porosity which is closely related of the coupled performance between heat conduction and groundwater heat advection.It is slow to recover the heat energy of the soil,so the GHE's heat transfer efficiency is weakened. There must be appropriate time of heat energy recovering, and the intermittent operation mode can satisfy this request. The GHE's heat transfer effect during summer and winter in the continuous operation mode and the intermittent operation mode is compared firstly, furthermore the soil recovering effect in the intermittent operation mode is analyzed, finally the heat recovering time which the soil demands in a system running period is researched. It supplies theory support and technology accumulation for the application of GSHP.