Convection heat transfer of supercritical CO2 in a single fracture in enhanced geothermal systems

Abstract EGS (Enhanced Geothermal System) is a potential way to utilize geothermal energy efficiently. In present work, a three-dimensional physical model, a single fracture with undulated surface morphology in hot dry rock is constructed. Supercritical CO2 is used as working fluid, and its convection heat transfer characteristics in fracture is numerically investigated. The influence of flow rate, inlet temperature, and reservoir pressure on convection heat transfer are probed. The results indicate that the local convection heat transfer coefficients at upper wall and lower wall of fracture show opposite variation trend at corresponding positions, and it varies with the undulation of surface morphology. In addition, the local convection heat transfer coefficients rise with the decrease of flow rate, the increase of pressure and inlet temperature. Furthermore, the correlation of normalized convection coefficient Nusselt number of supercritical CO2 in fracture is obtained.