Research On Influence Factors Of Heat Exchange Performance Of Vertical Tube

With the world energy problem getting nervous, shallow geothermal energy as anew type of high quality clean energy is getting the attention of more and morecountries in the world, especially in the United States and northern Europe somedeveloped countries. Shallow geothermal resources through the heat pump technologycan realize for building heating and cooling effect. Shallow geothermal resourcescombination with heat pump called ground source heat pump system. The ground heatexchanger is the core components of the system, which operation is good or not willinfluence the whole system normal operation and economy. Therefore, in order toensure the whole system economy and reliable operation, the reasonable design ofheat exchanger is especially important.The main influence factors of buried tube heat exchange performance aregeological and hydrogeological conditions, the thermal physical parameters of soiland construction conditions. This paper divided these factors into two categories:engineering factors and natural factors. Based on summarizing other scholars relevantinfluence factors of tube heat exchange performance, such as: buried tube method,borehole backfill and circulating fluid velocity, mainly analysis the initial temperatureof formation, aquifer thickness and groundwater seepage influence heat exchangeperformance.First of all, according to the regular of formation temperature from south to north,precede nine field thermal response tests, obtained the initial average temperature oflocal formation and the ability of heat exchanger heat absorb and release in winter andsummer. Then analysis with the reduce of formation temperature the heat transfer permeter of ground heat exchanger is increases in summer condition and decrease inwinter condition. When formation temperature more than20℃or less than5℃, needto increase the auxiliary equipment.Second, select six typical engineering examples in Yongding River alluvial fan,gotten coefficient of thermal conductivity and change of heat transfer per meterthrough calculation thermal response test data. Then analysis the influencing factorsof heat exchange performance in different situation. Those are the more groundwaterflow passes the pipe, the more enhance for heat exchange rate. And identify relatedequations of heat transfer per meter and aquifer thickness in Yongding River profile.Finally, a indoor comprehensive miniature test-bed of ground heat exchanger was built and analyzed the test data. Then concluded that the thermal conductivity andtemperature change range of three kinds hydrogeology conditions (dry sand, saturatedsand and groundwater seepage) are in turn increase. Groundwater seepage on theupper and lower respectively obstacles and promote soil temperature change. With theincrease of groundwater seepage velocity, groundwater brings more heat to further,and increase heat transfer.