Heat transfer characteristics of water flow through a single rock fracture: The combined effects of shear and surface roughness

Abstract

AbstractAn accurate understanding of the heat transfer of water through rock fractures is essential for the extraction and utilization of thermal energy from high‐temperature rock masses. A systematic numerical simulation based on the double‐rough‐walled model has been presented to investigate the shear effect on convective heat transfer in rough rock fractures. On the basis of the modified successive random additions algorithm, four different self‐affine surfaces were generated and utilized to establish the 3D double‐rough‐walled fracture models. The fluid flow and heat transfer were simulated by directly solving the Navier–Stokes equation and energy conservation equation, respectively. The combined effects of shear and surface roughness on the heat transfer were investigated. The results show that the heat within rough‐walled fractures transfers preferentially along the main fluid flow channels, and the areas of fast and slow thermal transmission fit well with the high‐ and low‐flow regions, respectively. As shear advances, the heat transfer coefficient firstly increases, then decreases slightly and finally stabilizes within a certain range, in which stabilization occurs earlier in fracture with a larger joint roughness coefficient. The effect of surface roughness on heat transfer shows an opposite trend during shearing. When the shear displacement is small, the enhancement effect of surface roughness that provides larger heat transfer areas dominates the heat transfer. As shear displacement continues to increase, this enhancement effect will be gradually weakened until the decreasing effect that bumps on the rough‐walled surface hinder the fluid flow dominates the heat transfer.