Study On Heat Extraction Performance Of Deep Borehole Heat Exchanger

With the rapid development of science and technology,people are demanding more and more energy,not only satisfied with food and clothing,but also pursuing energy conservation and environmental protection.From just enough food and clothing to the current pursuit of energy conservation and environmental protection.Therefore,at present,the development and utilization of new energy sources are becoming more and more important,while geothermal energy,as a clean,environmentally friendly and pollution-free new energy source,has gradually entered people's vision.In severe cold areas,extensive attention has been paid to the injection and exploitation of deep geothermal energy to realize winter heating of buildings.In order to inject and produce deep geothermal energy more reasonably and efficiently,this study conducted in-depth simulation calculation and analysis on the factors that affect the heat extraction of deep borehole heat exchanger.The main research work is as follows:1.Heat transfer analysis and heat transfer modeling are respectively carried out for the coaxial tubes and U-tube deep borehole heat exchanger.The finite difference method is used to divide the model efficiently.In the process of model calculation,the catch-up method is used,which not only saves a lot of calculation time,but also improves the calculation accuracy.2.The factors that affect the heat extraction performance of the coaxial tubes deep borehole heat exchanger are simulated and analyzed in depth.The results show that the smaller the thermal conductivity of the shallow backfill material is,the better the thermal conductivity of the deep backfill material is.When the heat load is 150 KW and the system has been running for 20 years,the influence range of temperature wave is 67.5m m.Therefore,the local geological conditions,heat extraction load and system operation timeshould be fully considered in the design of the coaxial tubes deep borehole heat exchanger.3.The factors affecting the heat extraction performance of U-tube deep borehole heat exchanger are simulated and compared with that of coaxial tubes deep borehole heat exchanger.The calculation results show that under certain geological conditions and heat load,the circulating water flow required by U-tube heat exchanger will be larger than that of coaxial tubes deep borehole heat exchanger,but the occupied area of U-tube heat exchanger is smaller than that of coaxial tubes deep borehole heat exchanger.4.According to the Fortran program,the design requirements for computer personnel are put forward for the coaxial tubes deep borehole heat exchanger which is widely used in practical engineering.It is compiled into the commercial software Geothermal Star II,and the help file of the software is written for the designer to carry out design calculation and simulation calculation.