Study On Heat Transfer Performance Of Vertical Double U Type Buried Tube Heat Exchanger Under Seepage

In the south of China,In East China,the energy consumption of cooling in summer is an important part of building energy consumption and occupies a large proportion in the total building energy consumption.How to achieve more energy saving and environmental protection in building cooling has become a hot topic.Compared with the traditional central air conditioning cooling,the ground source heat pump system has the advantages of high efficiency,energy saving,environmental protection and stability,and the heat transfer between the buried pipe and the soil is the key link of the ground source heat pump system.Therefore,it is very important to study the heat transfer performance of different factors on the ground source heat pump double U type pipe and the soil to reduce the energy conservation environment of the building.In view of the above situation,this paper mainly uses the FLUENT simulation software to study the influence of the groundwater seepage,the change of seepage velocity and the change of inlet velocity of buried pipe fluid on the soil temperature field and heat exchange of the double U type buried pipe in East China.In this paper,a mathematical model of a quasi three-dimensional double U type buried pipe and soil coupled heat storage is established.In the consideration of groundwater seepage in the soil surrounding the buried pipe,the soil surrounding the buried pipe is established as a porous medium model and the flow of groundwater seepage only along one direction is considered to be fixed at a fixed velocity.The main contents of the study are as follows:1)Use CATIA and ICEMCFD software to build three-dimensional mathematical model of underground pipe drilling and porous media model of underground soil.2)Use FLUENT software to divide and set up the corresponding boundary conditions.3)Simulate the distribution of the temperature distribution of the fluid at the velocity of 7x10^-7m/s,1x10^-6m/s and 5x10^-6m/s,the flow velocity of the fluid inlet is respectively 0.4m/s,0.9m/s and 1.4m/s,and the distribution cloud map of the temperature field of the underground soil is obtained.4)For the above 1 days and 15 days running for a short time respectively.The results show that:1)In the selected double U type buried pipe and the surrounding soil model parameters?whether there is groundwater seepage around the buried soil and the velocity of groundwater seepage?only changes the inlet velocity of the buried pipe fluid?from 0.4m/s to 1.4m/s?,the outlet temperature of the buried pipe increases with the increase of the inlet velocity of the fluid.For a fixed speed,the outlet temperature of the fluid starts to be the lowest and the initial temperature changes very fast,and then slowly changes little.2)Taking the inlet flow velocity of the double U type buried pipe fluid for 15 days as an example,when there is no groundwater seepage and groundwater seepage around the buried pipe and the seepage velocity is 7x10^-7m/s,1x10^-6m/s and 5x10^-6m/s respectively,the corresponding temperature difference between the inlet and outlet of the buried pipe is4.19K,5.12K,7.23K and 9.76K in turn,so the heat transfer of the double U embedded pipe and the surrounding soil under the four seepage conditions will be dependent on the heat transfer of the surrounding soil under the above four seepage conditions.It shows that the groundwater seepage around the buried pipe is more beneficial to the heat transfer between the buried pipe and the surrounding soil than that of the non groundwater seepage,and the greater the velocity of the groundwater percolation around the buried pipe,the greater the heat exchange between the buried pipe and the soil.3)By comparing the cloud map of the temperature field distribution around the buried pipe under the above situation,it can be seen that the heat accumulation near the double U type buried pipe is serious while the seepage velocity is 5x10^-6m/s,and the heat accumulation phenomenon is basically eliminated.It shows that the existence of soil groundwater seepage around the double U buried pipe is beneficial to reduce the heat accumulation near the buried pipe,and the greater the seepage speed is,the better the effect.