单井增强型地热系统性能分析

doi:10.16085/j.issn.1000-6613.2020-1285

摘要/Abstract

摘要：

为了解决深井换热器单井换热功率不高的问题，提出了一种单井增强型地热系统（single-well enhanced geothermal system，SEGS），SEGS通过在地热单井的钻孔周围建立人造热储来强化单井的换热能力。利用数值模拟的方式对SEGS进行了分析，研究了SEGS应用于建筑供暖的表现。结果表明：当换热流体采用由内管流入外管流出的流动方向布置形式时，SEGS的换热效果最好；此时单井单个供暖季平均换热功率为1603.6kW，是深井换热器的2.2倍。SEGS的换热功率随着人造热储半径的增大而增大，人造热储半径由50m提升至90m时，半径每增加10m带来的平均换热功率提升分别为102.7kW、67.0kW、43.8kW和29.2kW。单井换热功率随人造热储的厚度增加呈现先上升后略有下降的趋势，考虑到初投资问题建议热储厚度设计为400m。SEGS的换热功率随入口温度的降低以及入口流量的升高而增加。对于SEGS深度小于1500m的部分，需要考虑外管的保温。

关键词: 地热能, 深井换热器, 传热, 数值模拟, 多孔介质, 人造热储

Abstract:

In order to solve the problem of low heat transfer power of deep borehole heat exchanger, a single-well enhanced geothermal system (SEGS) was proposed. The SEGS enhances heat transfer capacity of a single geothermal well by establishing artificial heat storage around the borehole. The performance of SEGS used in building heating was studied by numerical simulation. The results showed that SEGS has the best heat transfer effect when the heat transfer fluid was arranged in the flow direction from the inner tube to the outer tube, the average heat transfer power of a single well heating system is 1603.6kW, which is 2.2 times of the deep borehole heat exchanger.The heat transfer power of SEGS increases with the increase of artificial heat storage radius. When the artificial heat storage radius increases from 50m to 90m, the average heat transfer power increase brought by every 10m increase in radius is 102.7kW, 67.0kW, 43.8kW and 29.2kW, respectively.With the increase of the thickness of artificial heat reservoir, the heat transfer power of single well presents a trend of first increased and then slightly decreased. Considering the initial investment, it is suggested that the thickness of artificial reservoir should be designed as 400m.The heat transfer power of SEGS increases with the decrease of inlet temperature and the increase of inlet flow. For parts with SEGS depth less than 1500m, the insulation of the outer tube should be considered.

Key words: geothermal energy, deep borehole heat exchanger, heat transfer, numerical simulation, porous media, artificial aquifer

中图分类号:

TK529

蒋坤卿, 黄思浩, 李华山, 卜宪标. 单井增强型地热系统性能分析[J]. 化工进展, 2021, 40(5): 2536-2545.

JIANG Kunqing, HUANG Sihao, LI Huashan, BU Xianbiao. Performance analysis of single well enhanced geothermal system[J]. Chemical Industry and Engineering Progress, 2021, 40(5): 2536-2545.

图/表 21

图1 SEGS结构

图2 导热模型模拟结果与试验结果对比

图3 试验砂箱

图4 多孔介质模型模拟与试验结果对比

图5 计算域

表1 物性参数

物质	密度/kg·m^-3	热导率/W·m^-1·K^-1	比热容/J·kg^-1·K^-1
水泥	2140	0.8	1900
岩石	2800	3.5	920
内管	910	0.21	1900
外管	8030	43.75	502.48
水	998.2	0.6	4182

表2 网格无关性验证结果

网格数量	出口温度/K
84234	307.92
105084	308.02
130284	308.03
231634	308.01
308334	308.01
535634	308.01

图6 SEGS和DBHE第一个供暖季换热功率随时间变化

图7 不同流向下供暖季末人造热储温度场变化情况

图8 两种地热井平均换热功率随时间的变化

图9 逆流形式SEGS第4供暖季末热储温度场变化

图10 第一供暖季末距井轴心0.5m处岩层温度变化情况

图11 不同固井水泥热导率下SEGS的换热功率随时间的变化

图12 不同热储厚度下SEGS的平均换热功率和出口水温

图13 不同热储半径的SEGS出口水温随时间的变化

图14 SEGS平均换热功率随热储半径的变化

图15 不同进口流量下SEGS的平均换热功率和出口温度

图16 内管平均出口温度随入口流量的变化

图17 不同入口流量条件下SEGS的增量变化情况

图18 SEGS平均出口水温和平均换热功率随入口水温的变化

图19 SEGS在不同进口温度下的逐日增量

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