多井同期抽灌储能模式咸水层热运移特性研究

Researche on heat transfer characteristics of brackish aquifers upon synchronization pumping and injection energy storage mode

基于含水层储能水、热运移的基本理论与控制方程,针对地下咸水层储能过程中渗流溶液密度及黏滞系数变化显著的特点,对现有的地下含水层储能数学模型进行修正、完善,建立地下咸水层耦合储能模型,探索不同储能模式下含水层温度场变化规律及阶段性热量运移特征。研究结果得到,采用地下原水与去离子水回灌时,在储热运行期与间歇停运期粗粉砂层中热作用半径变化率分别为0.272、0.008、0.348、-0.040m/d。在储能阶段,伴随回灌溶液温度上升、盐度降低,地下水渗流速度上升,导致对流传热与热弥散效应增强;间歇阶段,则由于地下咸水与回灌溶液间盐度梯度增大,在分子扩散作用下回灌溶液温度场影响范围减弱。

In order to revise and improve the current numerical model of energy storage and recovery system in aquifers, a three-dimensional coupled numerical model of groundwater flow and heat transfer and solute movement in brackish aquifers was established based upon the thermal and mass transfer in porous media, fully making use of the significant variation of groundwater density and viscosity coefficient in energy storage and recovery in brackish aquifer. The calibrated numerical model was used to explore into the thermal transfer characteristics and the variation regularity of the geo-temperature field in different energy storage modes. The numerical predictions indicate that the thermal radius changing rates are respectively 0.272, 0. 008, 0. 348 m/d, -0.040 m/d in the coarse silt aquifer when the original brackish solution and the deionization solution recharge during the heat storage period and the intermittent recovery period. The results also show that the seepage velocity of groundwater increases while the recharge solution salinity decreases and the temperature increases during the energy storage stage, which intensifies heat convection and thermal dispersion 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 radius of the infiltration solution in brackish aquifers.