Performance analysis of single well enhanced geothermal system

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

Abstract

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

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

CLC Number:

TK529

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.

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.

Figures/Tables 21

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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

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

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

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

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