为提高井底高温区地热能开采效率，文章构建了一种用于水平地热井开采的喷射式同轴套管换热器。基于有限体积法建立水平段近井底区三维数值仿真模型，对比分析外进内出型(Outside-in and Inside-out type，OI)、内进外出型(Inside-in and Outside-out type，IO)和喷射式(Jet Inlet，IOI)同轴套管换热器的流场和温度场，揭示了喷射式换热器强化传热机理。结果表明:IOI型换热器内流体的湍动能增加，并形成涡旋，提高了地热开采效率。通过对比采热性能发现，努塞尔数随质量流量增加而增加，IOI型的努塞尔数比其他两者分别高18。33%～32。48%和 5。33%～18。84%;摩擦系数随质量流量增加而降低;相同质量流量下，IOI型换热器热增强系数比其他两者分别高 9。13%～13。58%和 3。61%～10。24%;IOI型的平均采出温度和平均延米换热量始终在三者中最高。研究结果为提高水平地热井同轴套管式换热器开采效率提供理论依据。
Research on heat extraction characteristics of jet coaxial borehole heat exchanger
In order to improve the efficiency of geothermal energy extraction in the high-temperature zone at the bottom of the well,a jet-type coaxial borehole heat exchanger is constructed for horizontal geothermal well extraction.Based on the finite volume method,a three-dimensional numerical simulation model of the horizontal section near the bottom of the well is established,and the flow and temperature fields of the Outside-in and inside-out type(OI),Inside-out type(IO),and Jet inlet(IOI)coaxial borehole heat exchangers are compared and analyzed,so as to reveal the mechanism of the injection heat exchanger to strengthen the heat transfer.The results showed that the use of the IOI type heat exchanger increased the turbulent kinetic energy of the fluid and formed vortices,which improved the efficiency of geothermal heat extraction.By comparing the heat extraction performance,it was found that the Nusselt number increased with the increase of mass flow rate,and the Nusselt number of IOI type was higher than the other two by 18.33%～32.48%and 5.33%～18.84%,and the friction coefficient decreased with the increase of mass flow rate;under the same mass flow rate,the thermal enhancement factor of IOI type heat exchanger was higher than the other two by 9.13%～13.58%,3.61%～10.24%,and the average extraction temperature and average extended metre heat exchange are always the highest among the three.The results provide a theoretical basis for the efficient extraction of coaxial borehole heat exchanger in horizontal geothermal wells.
万方数据
维普
