既有地热单井采暖系统换热量的增强方法

ENHANCING HEAT TRANSFER METHODS OF EXISTING GEOTHERMAL SINGLE WELL HEATING SYSTEM

针对企业关注的单井换热量提高和优化运行问题,建立地热井内流体的流动换热方程和岩石的能量方程,并与热泵相结合,分析保温材料性能、注入水温度和流量对系统性能的影响。结果表明:地热井采出热功率随保温材料性能的增强而增大,保温材料导热系数从0.21 W/(m·K)减小到0.04 W/(m·K)时,地热井采出热功率从516.62 kW增加到543.92 kW;降低注入水温度可增大热泵输出功率,注入水温度为2.5、5.0、7.5和10.0℃时,地热井采出热功率分别为579.86、550.82、521.78、492.74 kW,热泵的输出功率分别为796.70、744.99、694.38、645.14 kW;井内对流热阻远小于岩石导热热阻,流量的增加对于提高换热量的作用较小。

To answer the enterprise’s concerns about heat transfer enhancement of geothermal single well and system optimization,a mathematical model for heat transfer between rock and geothermal well is developed.The effects of thermal insulation materials and temperature and velocity of injection water on the performance of heating system combined with heat pump are discussed.The results show that:The extraction heat power increases from 516.62 to 543.92 kW when the thermal conductivity of thermal insulation materials varies from 0.21 to 0.04 W/(m·K);The output power of heat pump can be enhanced by reducing injection water temperature.The extraction heat power and output power of heat pump are respectively 579.86,550.82,521.78,492.74 k W and 796.70,744.99,694.38,645.14 kW when injection water temperature is 2.5,5.0,7.5 and 10.0℃;The thermal resistance of convective heat transfer of geothermal fluid in well is far less than the conduction thermal resistance of rock.So,the flow rate of water has a very small influence on the heat transfer.