The heat transfer coefficient (HTC) is an important parameter describing the heat transfer characteristics between rock fracture walls and flowing fluid. This study summarizes and evaluates the existing typical overall heat transfer coefficient (OHTC) formulas (A - D) and proposes four new OHTC formulas (E - H). As a novelty different from the existing analytical methods, the new method solves the temperature distribution of a cylindrical rock sample in the form of integral, and thus obtains the expression of fracture surface temperature. Various experimental data were employed to evaluate each formula. The adaptability and stability of OHTC formulas are closely related to the flow rate. Based on the commonness of each formula, the key parameter affecting OHTC value is presented. Fluid flow and heat transfer in a single fracture is numerically modeled. Comparison of outlet water temperature obtained by numerical method and experimental measurement shows that the accuracy of formulas D, G and H is higher. For comparison with the parallel-plate model, the fractures with heterogeneous aperture are constructed, and heterogeneous HTC is adopted. The results show that the water temperature contours in fractures modeled with homogeneous HTC are more tortuous, and the temperature contours modeled with heterogeneous HTC are smoother. As the flow rate increases, the difference of outlet temperature between fractures with homogeneous and heterogeneous apertures increases.

传热系数（HTC）是描述岩石破裂壁与流动流体之间的传热特性的重要参数。本研究总结并评估了现有的典型总体传热系数（OHTC）公式（A-D），并提出了四个新的OHTC公式（E-H）。与现有的分析方法不同的是，该新方法解决了圆柱岩样温度分布的积分问题，从而获得了裂缝表面温度的表达式。各种实验数据用于评估每个公式。OHTC配方的适应性和稳定性与流速密切相关。基于每个公式的共同性，提出了影响OHTC值的关键参数。对单个裂缝中的流体流动和传热进行了数值建模。通过数值方法和实验测量得到的出水温度的比较表明，公式D，G和H的精度较高。为了与平行板模型进行比较，构造了具有非均质孔径的裂缝，并采用了非均质HTC。结果表明，采用均质HTC建模的裂缝中的水温曲线较为曲折，采用非均质HTC建模的裂缝中的水温曲线更平滑。随着流量的增加，具有均质孔和非均质孔的裂缝之间的出口温度差会增加。为了与平行板模型进行比较，构造了具有非均质孔径的裂缝，并采用了非均质HTC。结果表明，采用均质HTC建模的裂缝中的水温曲线较为曲折，采用非均质HTC建模的裂缝中的水温曲线更平滑。随着流量的增加，具有均质孔和非均质孔的裂缝之间的出口温度差会增加。为了与平行板模型进行比较，构造了具有非均质孔径的裂缝，并采用了非均质HTC。结果表明，采用均质HTC建模的裂缝中的水温曲线较为曲折，采用非均质HTC建模的裂缝中的水温曲线更平滑。随着流量的增加，具有均质孔和非均质孔的裂缝之间的出口温度差会增加。