【作者】 汪东林；

【导师】 高才；

【作者基本信息】 合肥工业大学 ， 动力工程（专业学位）， 2024， 硕士

【摘要】 在碳中和背景下,人们逐渐倾向于使用清洁能源。地热能储量丰富,利用简单,但目前大多数利用深度150米以内的地热能,热能储量较低,能源使用形式较为单一。中深层地热能储量较高,但是实际案例较少,理论依据较为缺乏,利用中深层地热能的核心是换热器,因此,对换热器进行研究分析十分重要。为此,本文采用数值模拟的方法,使用FLUENT软件,建立2000 m×88.5 m(井深×直径)的三维同轴套管式换热器模型,采用外管进内管出的换热方式,运行34 h,通过实验数据与模拟结果对比验证模型的正确性。首先,对两种换热方式进行参数敏感性分析,通过对温度场变化、渗流场变化、套管内流体温度变化分析,结果表明外管进内管出的换热方式出水温度更高、取热效果更好。再次,对外管进内管出的换热方式进行参数敏感性分析,通过控制变量法对地温梯度、岩土导热系数、注入温度、注入流速、外管导热系数和内管导热系数逐个分析,结果表明岩土导热系数、注入流速、内管导热系数变化对出口温度和换热量的影响较大,地温温度、注入温度对出口温度和换热量的影响次之,外管导热系数对出口温度和换热量的影响最小。最后,使用SPSS进行线性回归分析,得到出水温度的预测模型,同时计算了地温梯度、岩土导热系数、注入温度、注入流速、外管和内管导热系数对出水温度的贡献率,结果表明注入流速和内管的导热系数是两个最重要的影响因素。通过此研究得到的成果,可以对换热器进行有效优化,对于工程上寻找高效换热器具有重要意义。同轴换热器在设计阶段初期应采用低导热系数的内管,在运行阶段初期适当降低注入温度、增加注入流速,可有效提高出水温度,获得更高换热量。更多还原

【Abstract】 In the context of carbon neutrality,people gradually tend to use clean energy.Geothermal energy reserves are rich and simple to use,but at present,most of the use of geothermal energy within the depth of 150 meters,the thermal energy reserves are low,and the form of energy use is relatively single.The reserves of middle and deep geothermal energy are high,but the actual cases are few,and the theoretical basis is lacking.The core of the utilization of middle and deep geothermal energy is the heat exchanger.Therefore,it is very important to study and analyze the heat exchanger.For this reason,this paper adopts numerical simulation method and FLUENT software to establish a 3-dimensional coaxial tube heat exchanger model of 2000 m88.5 m(well depth diameter),adopts the heat transfer mode of the outer pipe in and out of the outer pipe,and runs for 34 h by comparing the experimental data and simulation results.First of all,the parameter sensitivity of the two heat transfer modes is analyzed.Through the analysis of temperature field change,seepage field change and fluid temperature change in the casing,the results show that the heat transfer mode in and out of the outer pipe has higher effluent temperature and better heat extraction effect.Again,the parameter sensitivity analysis of the outer tube,through the control variable method of geothermal gradient,geothermal temperature,injection temperature,injection velocity,outer tube thermal conductivity,the results show that the variation of soil,injection velocity,the inner tube thermal conductivity on the outlet temperature and heat change,geothermal temperature,injection temperature on the outlet temperature and heat change second,the outer tube thermal conductivity has the least influence on the outlet temperature and heat change.Finally,the linear regression analysis using SPSS obtained the prediction model of the effluent temperature and calculated the geothermal gradient,rock and soil thermal conductivity,the injection temperature,the injection flow rate and the thermal conductivity of the outer and inner tubes to the outlet temperature.The results show that the injection flow rate and the thermal conductivity of the inner tube are the two most important influencing factors.The results obtained from this study can optimize the heat exchanger effectively,which is of great significance for finding the highly efficient heat exchanger in engineering.In the coaxial heat exchanger,the inner tube with low thermal conductivity should be adopted in the early design stage to reduce the injection temperature and increase the injection flow rate in the initial operation stage,which can effectively improve the water temperature and obtain higher heat exchange.更多还原