A dynamic heat transfer coefficient between fractured rock and flowing fluid
A dynamic heat transfer coefficient between fractured rock and flowing fluid
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DOI：
10.1016/j.geothermics.2016.08.007
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发表时间：
2017
期刊：
影响因子：
3.9
通讯作者：
T. Heinze;Sahar Hamidi;B. Galvan
中科院分区：
文献类型：
--
作者：
T. Heinze;Sahar Hamidi;B. Galvan
地热产热量的估算仍然是地热行业面临的一大挑战。在连续介质力学中，模拟流体-岩石之间的热传递需要区分两种主要方法：局部热平衡(LTE)和局部热不平衡(LTNE)。虽然LTNE不需要强的瞬时局部热平衡假设，但岩石和流体之间的显式热传递参数只是粗略地定义。本文主要研究了岩壁与流动流体之间的换热系数。基于简单几何结构和稳态情形的实验装置，我们推导出了与裂缝开度、流速和热参数有关的动态换热系数。我们将我们的模型与实验数据进行了比较，在大多数温度下都达到了很好的一致性。与静态换热系数相比，动态换热系数改变了裂隙系统中流体和岩石的温度分布。然后，我们通过一个水库规模的模拟展示了我们的动态方法的可能扩展。与现有的模型和经验方法相反，我们的模型本质上适应了流场和温度场的空间异质性和时间变化。该模型基于定义明确的物理参数，这些参数可以很容易地从标准的实验室测试中获得，并依赖于速度和岩石温度等特征变量。我们的模型可以通过包含更多将渗透率、裂缝开度、流体压力和热传递联系在一起的本构关系来进行扩展。
Estimation of heat production remains a major challenge for geothermal industry. In continuum mechanics two main approaches need to be separated to model heat transfer between fluid and rock: local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE). While LTNE does not require the strong assumption of instantaneous local thermal equilibrium, the parameters for explicit heat transfer between rock and fluid are only loosely defined. This work focuses on the heat transfer coefficient between rock walls and flowing fluid. Based on an experimental setup with simple geometry and a steady state scenario, we derive a dynamic heat transfer coefficient dependent on fracture aperture, flow velocity and thermal parameters. We compare our model to experimental data and achieve a good agreement for most temperatures. In comparison to a static heat transfer coefficient, a dynamic coefficient changes the fluid and rock temperature distribution in the fractured system. We then show possible extensions of our dynamic approach with a simulation on reservoir scale. In opposite to existing models and empiric approaches our model intrinsically adjusts to spatial heterogeneity and temporal changes in flow and temperature field. The model is based on well-defined physical parameters which can be easily obtained from standard laboratory tests and dependent on characteristic variables like velocity and rock temperature. Our model can be extended by including more constitutive relationships linking permeability, fracture aperture, fluid pressure and heat transfer.