Abstract: 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.

Key words: enhanced geothermal system, JRC profile, convective heat transfer, rough single fracture