Experimental study of the heat transfer by water in rough fractures and the effect of fracture surface roughness on the heat transfer characteristics

•Rough fractures with different JRC values were created through 3D printing technique.•The effect of fracture aperture on the convective heat transfer was studied experimentally.•The JRC value is related to the convective heat transfer coefficient. An accurate understanding of the heat transfer of water flow through rough fractures is important for geothermal energy extraction and utilization. In this study, we used 3D printing to manufacture ten samples with joint roughness coefficient (JRC) values of the fracture surface ranging from 0–2 to 18–20 and conducted experimental investigations of the heat transfer characteristics of the water flow through the ten samples. The effects of the volumetric flow rate, the outer wall surface temperature, the JRC, and the fracture apertures on the heat transfer characteristics were determined. The results showed that a rougher fracture surface resulted in greater heat removal during the flow of the fluid through the rock surface.