Volume 66

Research on convective heat transfer mechanism of a rough single fracture in granite Bo Zhang, Yanlong Li, Tiankui Guo, Nengyou Wu, Zhanqing Qu

Abstract

Hot dry rock (HDR) is a deep geothermal resource with great potential and is clean and environmentally friendly. During HDR exploitation, it is necessary to form a penetrating heat transfer channel. Therefore, heat transfer in thermal reservoir has an important influence on the heat extraction of HDR. The rough single fracture is obtained by means of Brazilian splitting test, and the point-cloud data on the rough fracture is acquired by 3D laser scanner. The 2D rough single fracture convective heat transfer model is established by numerical simulation to analyze the convective heat transfer characteristics and carry out the Morris global sensitivity analysis. The results show that the outlet temperature and average heat transfer coefficient increase with the roughness increasing, and the local heat transfer coefficient is strongly correlated with the undulating and fluctuating degree. The increase of the average and local heat transfer coefficient is more obvious when the fracture aperture is larger (>40μm) or initial flow rate is higher (>50mm/s). This study can provide scientific basis for engineering design of enhanced geothermal systems.

Keywords Geothermal energy, Hot dry rock, Rough fracture, Numerical simulation, Heat transfer coefficient