Numerical investigation of fracture morphology effect on heat transfer characteristics of water flow through a single fracture

The understanding of fluid flow and heat transfer properties in fractured rock is still insufficient. This study numerically investigates the effect of fracture morphology on convective heat transfer between fracture surface and flowing fluid. Water flow and heat transfer in a single fracture with different degrees of surface roughness are simulated by a numerical model and compared with experimental data. Simulation results show that a rough surface enhances the heat transfer intensity compared with a smooth fracture. The water temperature at the outlet increases as the surface roughness increases. Water temperature in both rough fracture and smooth fracture increases nonlinearly along the flow direction. The temperature at the inner surface of the fracture fluctuates drastically where the fracture surface suddenly fluctuates. A morphology condition factor (MCF) is introduced to take into consideration the fracture morphology effect on heat transfer characteristics. A linear relationship between normalized MCF and normalized profile length can be observed. A model is proposed to describe variation of the MCF. The promoting effect of fracture surface roughness on heat transfer intensity is gradually reduced with the increase of flow rate.