Study Of The Effect Of Soil Seepage On Buried Pipe Heat Transfer Based On LBM

In practical engineering application,the design of ground source heat pump often ignores the influence of groundwater seepage on the heat transfer of buried pipe heat exchanger,but the influence of this aspect can’t be ignored.Therefore,this article will conduct numerical simulation of heat transfer between soil and ground heat exchanger from the mesoscopic level with no seepage and seepage condition,and to reveal the law of heat transfer.In this paper,a two-dimensional equivalent buried pipe physical model is constructed by using the quartet structure generation set（QSGS）.Secondly,the basic theory,relevant model and boundary conditions of the lattice Boltzmann method（LBM）are briefly introduced.The correctness and feasibility of the selected model was verified by simulating the correlation calculation example.Finally,the simulation of heat transfer of buried pipes without and with seepage is carried out by computer.The major work of the thesis as follows.（1）In this paper,five factors affecting heat transfer in buried pipe heat exchanger without seepage are discussed,including the type of medium in pore,porosity,distribution of particles in soil,thermal conductivity of soil skeleton and thermal conductivity of backfill material.The results show that under the condition of no seepage,the effective thermal conductivity of soil decreases exponentially with porosity,and increases exponentially with soil skeleton thermal conductivity.Increasing the looseness of the soil or the thermal conductivity of the medium in the pores can also increase the effective thermal conductivity of the soil.（2）This paper studies the influence of five factors on the heat transfer of buried pipe heat exchanger with seepage,including the porosity,seepage velocity,distribution of particles in soil,thermal conductivity of soil skeleton and thermal conductivity of backfill material.The results show that under the condition of other condition is constant,when the soil pore rate is less than or equal to 0.5,the initial seepage velocity is lower than 2 x 10^-6 m/s,the growth of nuclear distribution probability is greater than or equal to 0.02 or solid phase of soil thermal conductivity is greater than or equal to5.5 W/（m·K）of these four cases of any kind,the influence of seepage of buried tube heat exchanger can be ignored.When the influence of seepage can’t be ignored,the average temperature of the soil is always lower than that without seepage.The existence of seepage will often take away the heat near the buried pipe,which is conducive to eliminating"heat accumulation".The conclusions of this study could provide theoretical basis to optimize the design of the buried pipe structure.