Physical Modeling And Numerical Study On Flow And Heat Transfer In Sand-filled Fractured Rocks

The high radiation nuclear waste in underground repository releases heat to Surrounding rock, produce heat transfer, groundwater flow and the coupling effect between rock stress. Because all sorts of reasons fracture often exist in rock, when the local water contact waste and dissolve nuclides, through flow in rock fracture and achieve the consequences of radionuclide migration. So flow of groundwater in the fractured rock will directly affect block function of nuclear waste repository.Filled fractured rock is common in nature. To Study on flow and heat transfer in sand-filled fractured rocks, can more in-depth understanding the influences of flow of groundwater in the fractured rock nearby repository on radionuclide migration. Transforming no sand-filled fractured rock model, that was fabricated by using granite rock blocks taken from the Beishan area in Gansu province, which was being investigated as potential site for the high-nuclear waste repository in China.This experiment maked the vertical fractures filled with sands of grain diameters 0.5～0.63mm. Fluid flow and heat transfer experiments in different heat source temperature and contrast the results from no sand-filled fractured experiment. According to this experiment using software numerical simulated the experimental process and compared with the experimental results. And simulated the fractured rock under different operation conditions, summarizes the influence of different factors to flow and heat transfer of sand-filled Fractured Rocks.Analyzed the results and some main conclusion were educed:(1) On the basis of continuity equation and energy conservation equation, coupled TH governing equations of Saturated and sand-filled fractured rocks are derivated with giving up the assumption of Transient thermal equilibrium. Using the basic principle of heat transfer, and concludes that the method to calculate the time of transient thermal equilibrium in special units.(2) Sand had significantly influences to flow and heat transfer of sand-filled fractured rocks:Sands filled in the fractures enhanced the heat conduction of neighboring rock matrix, making the range of influence of the heat source larger than the unfilled fracture model, but the time for asymptotic steady-state getting shorter. Sands filled in the fractures are weakening the retardation of the heat transfer due to vertical fracture flow. (3) The experiment results reveal that for 120℃heat source temperature the steady-state temperature field was similar in pattern to that for 95℃heat source temperature. The range of influence of the heat source and the time for asymptotic steady-state temperature field increased with the heat source temperature.(4) The temperature field from the experiment was similar in pattern to that from the numerical simulation. However, some degree of boundary heat loss in the experiment was unavoidable, the measured temperatures were smaller than the numerical simulation results for adiabatic boundary conditions, and the differences increased with the heat source temperature. The retardation of the heat transfer due to vertical fracture flow was significant for higher water velocities and larger vertical fracture apertures. The influences of heat source temperature, the water velocity and aperture of the vertical fractures on the steady-state temperature of the model were significant.