Study Of Suitability Evaluation And Characteristic Change Of Aquifer Temperature Field In Groundwater Source Heat Pump In Shijiazhuang

As one of a central city of"Beijing-Tianjin-Hebei",Shijiazhuang is located in the strategic opportunities period of"Beijing-Tianjin-Hebei Coordinated Development",and in the port of ecological and atmospheric environment improvement,and there is an urgent need to develop and utilize clean and renewable energy.As an indispensable part of shallow geothermal energy development and application technology,groundwater source heat pump has the characteristics of low carbon,energy saving and high efficiency,and is widely used and promoted internationally.However,there are still blind selection site and well layout phenomena in the groundwater source heat pumps application actually.The phenomena resulted in insufficient water supply,recharge blockage and even"thermal breakthrough"during operation,which seriously affects the heat exchange efficiency of the unit and deteriorates the initial groundwater environment.Therefore,The paper aims to find alternative green energy sources in Shijiazhuang City.First,according to geological,hydrogeological conditions,groundwater dynamic conditions,groundwater chemical conditions,and environmental geological conditions,the suitability regions of groundwater source heat pumps in Shijiazhuang City is evaluated;And a three-dimensional hydrothermal coupling simulation model was constructed to analyze the change of aquifer temperature field under different well spacings and different pumping rates.This study provided a scientific and reasonable basis for the planning,development and utilization of groundwater source heat pumps in Shijiazhuang City.Through the research in this paper,the following conclusions:(1)The factors affecting the storage conditions,development and utilization,and operating efficiency of groundwater source heat pumps were analyzed,and the evaluation index system for the suitability of groundwater sources in Shijiazhuang was established.The suitability regions were evaluated by the fuzzy analytic hierarchy process combined with GIS.The evaluation results showed that:"The suitable region of groundwater source heat pump in the study area is 19.74km~2;the more suitable region is mainly distributed in the central area with an area of 251.22km~2;the unsuitable region is 66.71km~2."(2)Based on the suitability region evaluation of groundwater source heat pumps,a three-dimensional hydrothermal coupling simulation model was constructed using numerical simulation software to simulate the changes in the aquifer temperature field under different well spacings and different pumping rates.The simulation results showed that:when the well spacing is 50m,the pumping and filling flows are controlled below1750m~3/d,and the temperature field produced by reinjection well has a greater impact on the temperature of pumping well;when the well spacing is 60 m,the pumping and filling flows are controlled below 2250m~3/d,and the temperature field generated by the reinjection well will not have a great impact on the temperature of the pumping well;when the well spacing of the pumping and filling wells is 70m,the pumping and filling volume should be controlled at 2750m~3/d to avoid"thermal breakthrough.".(3)The migration speed of the cold front produced by the filling well and its influence on the pumping well are controlled by the pumping water yield and well spacing.The larger the pumping water yield,the stronger the hydrodynamic field generated by the pumping well,and the cold front will gather towards the pumping well.The faster the speed;the larger the corresponding well spacing,the less the mining well is affected by the cold front.