| Under the background of energy consumption and environmental population, shallowgeothermal energy with its clean non-population and renewable advantage, the variouscountries positive quickly promotion and the use of a large area of new energy. Groundwatersource heat pump mining energy technology is widely promoted and exploited because of itsability effectively use of energy and reduce air environmental pollution caused by the use of toomuch conventional energy. As the heat exchange carrier, the change of groundwatertemperature has a great impact on the operating efficiency of the groundwater source heat pumpsystem. Therefore, studying the aquifer temperature field distribution characteristics and theevolution law is essential, which should be the premise and foundation of a groundwater sourceheat pump mining technology popularization and application. Based on the water temperatureand ground temperature observation data, this study system analyses the shallow geothermalfield distribution characteristics and main influencing factors in Xi’an, as well as its changecharacteristics in the process of the shallow geothermal energy development and utilization.Based on the Xi’an Jinghe Development Zone of a groundwater source heat pump systemdesign, groundwater seepage and heat migration couppled model is built. It is calculated by theHST3D heat transfer software, finally, the shallow geothermal field development and changescharacteristics under the conditions of the different recharge ratio and well spacing water isstudied. The conclusions are as follows:⑴The geothermal gradient ranges from0.77~5.38℃/100m in Xi’an, and the averagegeothermal gradient is3.11℃/100m. The surface current value ranges from22.77~107.33MW/m2, and the higher surface current value shows that the lithosphere isrelatively thin and the presence of fault in the region. Under the influence of the structuralfaults, the northwest, central and southeastern geothermal gradient high value areas areformed.⑵The characteristics of plane ground temperature distribution is that the central regionhas the highest temperature, followed by the north and south region, and the eastern region hasthe lowest temperature. And in the vertical direction, the ground temperature under theconstant temperature zone increases with depth, and its change forms are broadly divided into gradient heating form and alternate heating and cooling form. However, the gradient heatingtype is the main change form.⑶The distribution of the shallow geothermal field is basically consistent with the strikeof major active faults in the area，mainly controlled by new tectonic movement. In addition，groundwater and the litho logy and structure of rock and soil are also important influencingfactors.⑷On the assumption that the system100%recharges, in the case of the larger wellspacing, the time of pumping well happening "hot break" is extended and the groundwatertemperature amplitude of pumping wells is relatively smaller after five years of continuousoperation.⑸On the assumption that the well spacing is70meters, recharge amount has asignificant effect on the underground temperature field, and the effect is shown as the time ofpumping well happening "hot break" being shortened with the increase in the amount ofrecharge, so the actual project should try to avoid using large recharge operation.⑹Therefore, for water source heat pump system, the best run programs would be thatin the case of which, the flow and temperature field affected range is as small as possible andthe " hot break " time is as late as possible, so the heat pump system can operate efficiently tosave energy. In addition, in the end of an operation cycle groundwater temperature can returnto the initial one to have minimal impact on the operating efficiency of heat pump system. |
PDF Full Text Request