Three-dimensional Numerical Simulation Of Geothermal Field For Multi-buried Pipes Under Condition Of Coupled Thermal Conductivity And Groundwater Seepage

The ground source heat pump takes the soil as a cold and heat source,and utilizes little electricity to heat and cool the building,which has good energy saving and environmental benefits.The vertical ground source heat pump buried the closed buried pipes in the rock and soil through vertical borehole to exchange heat with the soil.The seepage of groundwater is often found in the strata through which the buried pipes pass.Establishing a more accurate buried pipes heat transfer model and performing reliable simulation calculations are the basis for rationally designing ground-buried pipes.After a long-term operation,the temperature field of the formation determines the reliability of the system during its life cycle.Groundwater seepage and heat transfer in the soil are coupled.The heat transfer between the buried pipes in the buried pipe group also influences each other.The influence of a single borehole on the temperature field is not the same as that of the ground pipe group and the temperature field is very different.This paper studies the influence of seepage and multi-buried pipes on the temperature field of the formation.The work undertook in this paper and the results achieved include:1.The mathematics control equations of coupled heat transfer and groundwater seepage of buried pipe group in the aquifer are given.Based on the control equation and the non-isothermal pipe flow module in the finite element numerical simulation software COMSOL,a simplified physical model of the buried pipe is established.2.Based on the finite element numerical simulation software COMSOL,the accuracy of the simplified model was verified using sandbox test data and on-site thermal response test data.3.Three-dimensional numerical model for coupled heat transfer and groundwater seepage in an aquifer was established.4.The temperature field of the aquifer after one year’s operation was studied,and the effects of different hydraulic conditions on the temperature field of the formation and the outlet temperature of the buried pipe were compared and analyzed.The study showed that the established simplified model of ground pipe had a good applicability to the calculation of coupled heat transfer in large-scale buried pipe groups.Groundwater seepage could improve the heat transfer efficiency.Disposing the buried pipe group along the direction of seepage could reduce the mutual influence between buried pipes.