单井地热供暖关键因素分析

Analysis of key factors affecting single well geothermal heating

基于地热井内流体的流动换热方程以及岩石的能量方程,研究井直径、岩石导热系数、井深和地温梯度对采出水温度和采热功率的影响.结果表明:单井采出水温度、采热功率和岩石温度场均随时间衰减,第1、10、20个供暖季对应的平均采热功率分别为755.01、660.02、639.42 kW,上述数据可用于热泵选型.对于20 a的供暖期,当两井间距为200 m时不会产生热干扰;岩石导热热阻远大于井内对流热阻和井壁导热热阻,降低岩石的导热热阻是提高采热功率的最有效手段;增加井直径和岩石导热系数可以降低岩石导热热阻;岩石导热系数每增加0.5 W/(m·K),采热功率增加100 kW;增加地温梯度和井深可以增大岩石和流体之间的传热温差,提高采热功率;地温梯度每增加10 K/km,采热功率增加213.54 kW.

The effects of well diameter, rock thermal conductivity, well depth and geothermal gradient on produced water temperature and extraction heat power were studied based on the mathematical equations for flow heat transfer and rock energy in geothermal well. Results showed that the produced water temperature, extraction heat power and rock temperature field always reduced with time. The average extraction heat power was respectively 755.01, 660.02 and 639.42 kW for the first, tenth and twentieth heating seasons, and the above data can be used for the type selection of heat pump. The spacing of 200 m can avoid thermal disturbance among the wells with heating time of 20 years. The rock thermal conduction resistance was far greater than the fluid convection heat resistance and the well wall thermal conduction resistance, so reducing rock thermal conduction resistance was the most effective method for increasing extraction heat power. The rock thermal conduction resistance can be reduced by increasing the well diameter and the rock thermal conductivity. The extraction heat power can increase 100 kW with the increase of rock thermal conductivity of 0.5 W/(m·K). The temperature difference between liquid and rock can be raised by increasing geothermal gradient and well depth, and thus leading to the increase in extraction heat power. The extraction heat power can increase 213.54 kW with the increase of geothermal gradient of 10 K/km.