多孔介质中沉积颗粒脱离特性试验研究

开展沉积颗粒在多孔介质中脱离过程试验对研究地下水源热泵回灌堵塞过程有重要意义。利用自主研发的砂层沉积–脱离模拟试验系统,研究增加渗流速度和改变渗流方向对多孔介质中已沉积颗粒脱离特性的影响。结果表明:在改变渗流速度大小条件下,渗流速度越大,已沉积的颗粒越容易发生脱离,到达悬浮颗粒相对浓度第二次峰值所需的时间越短,而达到二次峰值时所注入的水量接近;与改变渗流速度大小相比,用改变渗流方向的方式进行沉积颗粒脱离效果更为明显,到达二次峰值所需时间更短、水量更少,但随着时间增加,多孔介质中又会出现类似渗流方向改变前的堵塞现象;渗流条件变化后的初始阶段是已沉积颗粒脱离的主要时期。研究结果为水源热泵回灌过程中悬浮颗粒在地层中的沉积-脱离特性进一步研究奠定了基础。

Experimental research on release characteristics of deposited particles in porous media

The experimental research on the release characteristics of deposited particles in porous media plays an important role in the blocking process of the WSHP recharge. The release characteristics of deposited particles in porous media are studied by using the self-development sand deposition and release equipment. Two factors are taken into consideration, one is increasing the flow velocity, the other is changing the flow direction. The study shows that as the flow velocity increases, deposited particles are easier to release from the surface of porous media and it takes less time to reach the second peak of relative concentration, meanwhile, the water injected is almost of the same amount. Compared with the way of increasing the flow velocity, the way of changing the flow direction is more effective in the releasing process of deposited particles, and it takes less time and water to reach the second peak of relative concentration. With the increase of time, blocking will appear in porous media and change as it is before the flow direction. The initial phase after the flow condition changes plays an important role in the release of deposited particles. The research lays foundation for further studies on the deposition and release characteristics that suspended particles transport in layer, especially in the recharge process of WSHP.