Research On Improving The Heat Exchange Performance Of Underground Pipes Of Ground Source Heat Pump System

In this paper,the single U-type vertical ground heat exchanger is taken as the research object,and the ANSYS simulation software is used to establish the three-dimensional model of the single U-type ground heat exchanger with the same size as the actual project.The numerical simulation of the ground source heat pump system in heating season is carried out by Fluent simulation.The geological conditions of the local soil were obtained through the land thermal response experiment of the measured project,and the correctness and accuracy of the model were verified by the measured data.The influence of five factors on heat transfer performance of buried pipe was analyzed.The results show that the buried pipe depth,backfill material,groundwater seepage,seepage velocity and porosity of seepage zone have certain influence on the heat transfer of buried pipe.The influence of five factors on the heat transfer efficiency of ground source heat pump system is analyzed and the reasons for this influence are theoretically explained.Finally,the operation effect of the actual system is analyzed and evaluated,and the design reference is provided for other similar practical projects.His specific findings are as follows:the static investment recovery period of the project is about 8.14 years;annual operation can reduce carbon dioxide emissions1059.839 tons,reduce sulfur dioxide emissions 8.581 tons,reduce dust emissions 4.290tons.According to the research on influencing factors,it is found that when the buried pipe depth increases from 80m to 100m,the total heat transfer increases by 15%and 9%respectively,but the heat transfer of single well decreases.When the backfill material is clay,sandy soil and sandstone,the single well heat transfer increases by 2.1%and 0.08%respectively.The larger the backfill thermal conductivity is,the better the heat transfer performance is.The heat exchange capacity of single well with seepage condition is increased by about 34.25%compared with that without seepage condition.Groundwater seepage can greatly improve the heat transfer performance of buried pipes.When the soil porosity was 0.3,0.4 and 0.5,the heat transfer decreased by 15%and 7.2%respectively.The smaller the porosity was,the better the heat transfer was.When the seepage velocity is 4x10^-5m/s,6x10^-5m/s and 8x10^-5m/s,the heat transfer increases by 5.09%and 2.56%respectively.The faster the groundwater seepage velocity is,the better the heat transfer of the buried pipe is.