团队博士关于中深层地埋管长期热作用下地温场演变规律的研究发表于最具期刊 Geothermics。

Dr. Ma Zhendi published a paper titled “Investigation on local geothermal energy attenuation after long-term operation of ground heat exchanger with considering aquifer effect” in Geothermics.

本文探究了在中深层地埋换热器长期取热下，含水层对换热器周围地热能衰减的影响。在中深层地埋换热器长期运行下，不断从岩土中取热，会导致其周围岩土中地热能的衰减。受地埋换热器取热影响的岩土区域的地热能随时间的变化是一个值得专门研究的课题。本文建立了地埋换热器与周围含水层、隔水层等地质层之间的传热模型，并进行了数值求解，研究了地埋换热器性能的变化及地温场的衰减行为。结果表明:由于地下水在含水层中流动所导致的对流换热，含水层和隔水层中地埋换热器第8年的性能与第1年相比的降低率分别为1.3%和8.9%。对周围岩土的温度变化分析表明，地下水流动导致含水层中换热器周围的地温变化呈现周向不对称性，并且进一步影响了隔水层中地埋换热器周围的温度分布。对于隔水层来说，含水层的钻孔壁的温度恢复最差；而对于含水层来说，含水层下游的一个固定位置的地温恢复最差。以瞬时地温和初始地温的差值大于0.5℃为阈值表征衰减区域，含水层中第8年地热能的衰减面积约为第1年的4.5倍，隔水层中约为第1年的5.1-5.5倍。通过对地埋换热器的取热性能和地温场变化的分析，定量评价了地埋换热器长期运行下含水层和隔水层中地热能的衰减情况。

This paper investigated the local geothermal energy attenuation after long-term operation of ground heat exchanger with considering aquifer effect. The long-term operation of deep buried ground heat exchangers (GHE) for heat extraction would attenuate the local geothermal field. The variation of geothermal energy in the affected area over time is a subject worthy of dedicated study. In this paper, the heat transfer between GHE and surrounding geological strata including aquifuge and aquifer layers is modeled and numerically solved to investigate the variations of GHE performance and attenuation behaviors of ground temperature field. The results show that the reduction ratios of GHE performance in the aquifer and aquifuge layers between 1st and 8th years are 1.3% and 8.9%, respectively, due to the convective heat transfer induced by groundwater in the aquifer layer. The analysis of local temperature variation implies that the groundwater flow leads to the circumferential asymmetry of ground temperature reduction in aquifer layer, which also affects the temperature distribution in geological layers adjacent to the aquifer. The worst ground temperature recovery point appears on the borehole wall in the aquifuge layer, while it appears at a fixed position downstream in the aquifer layer. Taking the ground transient and initial temperature difference greater than 0.5℃ as the threshold to characterize the attenuation region, the geothermal field attenuation area of the eighth year in the aquifer is about 4.5 times that of the first year, while it is about 5.1 ~ 5.5 times that of the first year in the aquifuge layers. The analysis of variations of GHE performance and ground temperature field quantitatively evaluates geothermal attenuation behaviors in aquifer and aquifuge layers subject to the long-term operation of GHEs.

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Fig. 13 The isotherms of T(t) -T(0) = 0.5℃ in the aquifer and aquifuge layers (a) at the end of 88th month, and (b) at the end of 96th month.

文章链接：http://doi.org/10.1016/j.geothermics.2022.102608