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Author(s) :

Ma Jiuchen, Ma Jiuchen, Lyu Linhai, Yang Jie, Cui Afeng, Wei Fan.

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Abstract :

Abstract: Taking the multiple moving finite line heat sources（MFLS） operation mode as the research object, the unsteady state analytical solutions of the excess temperature in aquifer ΔTMFLS are obtained by applying space-time superposition principle, based upon the transient moving finite line heat source model. A calculation model coupled lattice Boltzmann method （LBM） and ΔTMFLS is established, according to introduce the discrete force source term into the Lattice Bhatnagar-Gross-Krook （LBGK） evolution equation of the velocity distribution function. The coupled model and the calculation method are validated by the data determined from the in-situ thermal re-sponse test. The results show that coupled LBM-ΔTMFLS simulation can well reproduce the evolution process of seepage velocity in aquifer which presents four successive stages of starting, declining, rising and stabilizing. With the decreasing of the porosity of aquifer, the movement space of virtual fluid particles reduces, consequently the collision probability of inter-particles and between particles and porous media increases, which leads to the kinetic energy loss enhancing, the descend range of seepage velocity increasing, and the recovery process retarding. While the inflow velocity increases, however, the influence degree of porosity on the hydrodynamic evolution of aquifer weakens. Meanwhile the directivity of the heat transport process in the aquifer enhances significantly. Key words: geothermal energy, heat transfer, porous media, numerical models, aquifers, lattice Boltzmann method 摘要： 基于有限长移动线热源（MFLS）传热模型,根据时空叠加原理推导出含水层非稳态过余温度解析解ΔTMFLS;在格子单松弛模型（LBGK）的演化方程中引入离散力源项,建立格子Boltzmann法（LBM）与ΔTMFLS的耦合计算模型。通过热响应实验,验证耦合计算模型与求解方法的正确性。研究表明,在不同计算工况下含水层各区域的渗流速度均具有启动—下降—回升—稳定的4个连续阶段。随着含水层孔隙率的降低,虚拟流体粒子动能损失增大,渗流速度降幅增大,回升过程缓慢。然而随着进水流速的提高,孔隙率的变化对于含水层水动力场演化过程的影响程度减弱;含水层热量运移过程的方向性显著增强。 关键词: 地热能, 传热, 多孔介质, 数值模型, 含水层, 格子Boltzmann方法

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