花岗岩粗糙单裂隙对流换热特性的数值模拟

在干热岩储层中开采地热能，往往需要对储层进行人工水力压裂以形成贯穿的换热通道。然而，热储中的对流换热对干热岩的采热率有重要影响，经过人工刺激的储层会形成几何形态各异的裂隙面，而裂隙粗糙程度的不同则会引起换热性能的显著差异。因此，选取4条Barton的经典岩石裂隙粗糙度曲线，在试验室条件下建立一个单裂隙对流换热模型。详细分析了花岗岩粗糙裂隙中热工质的换热特性。结果表明：局部对流换热系数沿着裂隙长度方向逐渐降低；节理粗糙系数JRC值越大，平均对流换热系数就越大，表明换热性能越好；局部对流换热系数的分布与JRC曲线的几何轮廓形态有很好的相关性，波峰波谷的变化趋势相一致；相对于温度而言，高流速对局部对流换热系数具有放大效应，流速越大，局部对流换热系数波动越大。

Numerical simulation of convective heat transfer characteristics of a rough single fracture in granite

In order to exploit geothermal energy in dry hot rock reservoirs, it is often necessary to conduct artificial hydraulic fracturing to form a penetrating heat transfer channel. However, convective heat transfer in thermal reservoir has an important influence on the heat extraction rate of dry hot rock. Artificially stimulated reservoirs will form fracture surfaces with different geometric shapes, while different roughness of fractures will cause significant differences in heat transfer performance. Hence, this study selects four Barton's classical rock fracture roughness profile to establishe a single-fracture convective heat transfer model under laboratory conditions, and to analyze the heat transfer characteristics of the hot working fluid in granite rough fracture in detail. The results show that the local convective heat transfer coefficient decreases gradually along the fracture length direction. The average convective heat transfer coefficient increases with the increase of joint roughness coefficient (JRC), which indicates that the heat transfer performance is better. The distribution of local convective heat transfer coefficient is well correlated with the geometric profile of JRC curve, that is, the variation trends of wave crest and trough of the two curves are consistent. Relative to temperature, the high flow velocity enlarges the local convective heat transfer coefficient, which indicates that the greater the velocity is, the greater the fluctuation of the local convective heat transfer coefficient is.