Research On Influencing Factors Of Performance Of Underground Heat Exchanger Of Ground Source Heat Pump

With the development of the times,people’s demand for energy is growing,the use of traditional fossil fuels will not only cause pollution to the environment,but also difficult to regenerate,will gradually be replaced by new energy sources,and geothermal energy as a clean,renewable new energy has gradually been paid attention to,soil source heat pump technology as a new technology using geothermal energy,widely used in the world,domestic and foreign scholars on the soil source heat pump research is also more and more.However,there is not much comprehensive analysis of single and dual U-type buried pipe system and surrounding soil temperature distribution,and this paper combines the research results of domestic and foreign scholars to further study the heat exchange process of single and dual U-type buried pipe system and surrounding soil system by setting up a test bench and establishing a numerical model of vertical buried pipe.The actual data measured by the test bench are verified by combining the results of the three-dimensional model of the numerically buried tube heat exchanger.In this paper,a small test bench for the buried pipe system is set up,because the summer heat storage mode is similar to the winter heat storage mode,so this paper only studies the heat exchange process of soil in the summer heat storage mode.Different buried pipe forms,its heat exchange characteristics are necessarily different,for two different buried pipe forms of vertical buried pipe heat exchanger,to explore the different operating conditions of its heat exchange performance and two forms of ground buried pipe heat exchanger on the surrounding soil is the focus of this paper.The following tests were carried out on the two vertical buried tube heat exchangers:import temperature,inlet flow rate,intermittent operation mode,pipe diameter and seepage state on the heat exchange performance of single and double U buried pipes and the distribution of surrounding soil temperature.Under the conditions of this test,it is concluded that the increase of the temperature of the imported fluid promotes the heat exchange process of the buried pipe system and the soil system to a certain extent,and the outlet temperature of the double U tube is higher than that of the single U tube in the single and double U tube continuous operation mode,which is 28 degrees C,32 degrees C and 36 degrees C,respectively.With the increase of inlet flow rate,the heat exchange capacity of single and dual U tubes is also improved.When the import flow rate of single and double U tube is the same,the outlet temperature of double U tube is higher than that of single U tube,and there is no obvious difference between the change of the flow rate in the tube and the disturbance of soil temperature.The deep heat exchange of the buried pipe system unit decreases with the increase of the running time,the longer the intermittent operation time,the closer the soil temperature is to the initial temperature,the better the heat exchange energy of the ground buried pipe system,the average recovery rate of the soil temperature decreases with the increase of the distance from the center of the buried pipe,and the radius of the soil affected by heat is judged to be about 600 mm within 24 h.Under the conditions of 25 mm,32mm and 40 mm respectively,the unit depth of the single U tube is 32 mm,the smallest is 40 mm,and the unit depth of the double U pipe is with the The increase of the buried pipe diameter decreases in turn,and under the same operating conditions,the soil temperature around the single-double U-tube is higher than that of the single U-tube through the measured data of the soil measuring point at the pipe wall,and the temperature difference is about0.84 degrees C.In the seepage state,the process of soil temperature recovery is accelerated at the same time improves the heat exchange effect of the buried pipe system,the greater the seepage speed,the more obvious the heat exchange effect,in the seepage state,after running 8h,the temperature of different measuring points in the sand tank has changed,and with the increase of seepage speed,the soil temperature change is less obvious.Then,Then,according to the actual size of the test bench set up to establish a threedimensional model,simulate vertical buried pipe heat exchanger underground soil heat transfer process and compare the simulation results with the actual data obtained from the test,after the error analysis of the two,the results of the test measured data and simulation,although there is an error,but within the scope allowed by the project,and the temperature change trend of the two is similar,it can be considered that the simulation is a more accurate reaction test conditions.The experimental research of this paper is mainly to provide reference for the application of buried pipe system in practical engineering.