Influence of Recharge Solution Salinity upon the Thermal Transfer Characteristics in Energy Storage Superficial Brackish Aquifers

Due to the hydrogeologic particularity of brackish aquifers,a three-dimensional couple numerical model of groundwater flow and heat transferring and solute movement in brackish aquifers was established based upon the thermal and mass transferring in porous media. The calibrated numerical model was used to probe into the thermal transfer characteristics and the variation regularity of the geo-temperature field in different modes of recharge solution salinity with the brackish aquifer energy storage system in Tianjin as an example. The simulated calculation indicates that the change rate of the thermal effects radius is 0. 313,-0. 016.0. 348,-0. 04 m / d in the coarse silt aquifer when the 1∶ 1 mixed solution and the deionization solution recharge during the heat storage period of summer and the intermittent recovery period of next spring separately. The results show that the seepage velocity of groundwater increases while the recharge solution salinity decreases during the energy storage stage,which intensifies heat convection and thermodispersion and then increases the influence scope and range of the recharge solution temperature field. During the intermittent stage,the salinity gradient between the original brackish solution and solution recharge becomes larger when the injection salinity decreases and the mechanical dispersion capability becomes stronger,which shrinks the thermal effects radius of the infiltration solution in brackish aquifers.