Numerical Modelling of a Sedimentation Tank for Enhancing Sediment Removal in Open-Loop Ground Source Heat Pump System of Type Standing Column Well

Standing column wells are open-loop ground source heat pump systems that directly use groundwater as heat transfer medium. Usually, these wells are coupled with an injection well to enhance the advection process and thus the geothermal system efficiency during peak power periods. Due to the sediment load that may be present in groundwater, reinjected water tends to clog the aquifer, making it less permeable and, in the worst case, leading to undesirable overflows. To avoid this problem, we introduce a rectangular sedimentation tank placed before the injection well to retain sediments before reinjecting the water into the aquifer. To assess the feasibility of this solution, a numerical model has been set up, based on common hydraulic conditions properties such as particle size and concentration. The fluid dynamics and settling process have been coupled and simulated with the mixture model, which has been determined appropriate for the modelling conditions encountered. Based on this model, different tank geometries were tested to maximize sediment removal. Results show that tank efficiency can be improved by up to 37% for a given geometry and particle size, resulting in a noticeable reduction in sediment concentration in groundwater returned to the aquifer at a constant temperature.