Conjugated Numerical Approach for Modelling DBHE in High Geothermal Gradient Environments
Conjugated Numerical Approach for Modelling DBHE in High Geothermal Gradient Environments
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DOI：
10.3390/en13226107
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发表时间：
2020-11
期刊：
影响因子：
3.2
通讯作者：
T. Renaud;P. G. Verdin;G. Falcone
中科院分区：
文献类型：
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作者：
T. Renaud;P. G. Verdin;G. Falcone
地热是一种可再生能源，可以通过各种地下技术进行开发。封闭地热井解决方案，如深层地热热交换器（DBHEs），包括循环工作流体以回收可用热量，与传统地热系统相比，对当地地质环境的依赖较小。本文强调采用双数值方法来加强对DBHE性能的评价。利用计算流体动力学（CFD）商业软件和1D井储耦合地热模拟器T2Well，研究了高地温梯度环境下垂直DBHE的传热和流体流动。使用恒定的水性质来研究DBHEs产生的能量可能会导致低估高温和低质量流量下的总体传热。二维轴对称CFD模型提高了对DBHE底部回流的理解，重新调整并更好地估计了通常使用一维模型获得的压力损失。本文强调了DBHE内油管底部存在对流细胞，由于注入水量的增加，对流细胞的影响不明显。这两个代码都显示了限制数值限制，以获得高地温梯度环境中dbh地热提取的真正潜力，并证明它们可以用于地热能工程应用。
Geothermal is a renewable energy source that can be untapped through various subsurface technologies. Closed geothermal well solutions, such as deep geothermal heat exchangers (DBHEs), consist of circulating a working fluid to recover the available heat, with less dependency on the local geological settings than conventional geothermal systems. This paper emphasizes a double numerical method to strengthen the assessment of DBHE performances. A computational fluid dynamics (CFD) commercial software and the 1D coupled wellbore-reservoir geothermal simulator T2Well have been used to investigate the heat transfer and fluid flow in a vertical DBHE in high geothermal gradient environments. The use of constant water properties to investigate the energy produced from DBHEs can lead to underestimating the overall heat transfer at high temperature and low mass flow rate. 2D axisymmetric CFD modelling improves the understanding of the return flow at the bottom of the DBHE, readjusting and better estimating the pressures losses commonly obtained with 1D modelling. This paper highlights the existence of convective cells located at the bottom of the DBHE internal tubing, with no significant effects due to the increase of injected water flow. Both codes are shown to constrain the numerical limitations to access the true potential of geothermal heat extraction from DBHEs in high geothermal gradient environments and demonstrate that they can be used for geothermal energy engineering applications.