An Experimental Study Of Particle Deposition At The Fluid/Porous Media Interface Under Various Fluid Velocities

Deposition and aggregation of suspended particles in porous media widely occurs in natural and many industrial processes when fluid thorough porous media,such as particle clogging during geothermal reinjection,silt accumulation in river bed,plugging in filter layer of pumping wall,scaling at rough surface of heat exchanger,as well as contaminant adsorption in groundwater environment,involving fluid mechanics,heat transfer,hydrogeology and many other fields,a common feature of these physical phenomena is the particle deposition at the fluid/porous media interfaces during migration In this paper,clogging during geothermal water injected into sandstone being taken as research background,particle deposition at the fluid/porous media interfaces was experimentally studied under various temperature gradients at the interfaces and fluid velocities.Previous studies have been focused on the particle deposited inside porous media,few studies have been done on the deposition properties of micro-particles at the interface of porous media,while the temperature gradients at the interface are less studied.In this paper,two laboratory systems for the particle deposition at the interface of porous media with temperature gradients and under various fluid flow rates are set up respectively.The effect of the temperature gradient and the flow rate on particle deposition were compared.The conclusions are as follows:(1)The temperature gradients at the interfaces affect particle deposition,,the deposition amount of particles under temperature gradient condition is larger than the condition without temperature gradients,and the deposition amount increases with the temperature gradient increasing.This is because the Stk number of the particles is smaller under steady-state conditions,particles are more affected by diffusion during deposition and are more likely to be carried together by the fluid.However,the fluid properties change when temperature gradient exists at the interface,Stk number increases,thus the inertial force of the particles in increases and the deposition amount of particles increases accordingly.In addition,temperature gradient at the interface leads to a difference in the density of the fluid,resulting in natural convection,causing a change in the amount of particle deposition.(2)The amount of particle deposition decreases with the increase of the fluid flow rate,the amount of particle deposition decreased.This is because the larger the flow velocity,the greater the entrainment of the particles by the fluid,and the more particles are entrained.At the same time,the flow rate increases,the particle force increases,the deposited particles may partially rebound,resulting in a reduction of its deposition.The amount of particle deposition decreases as the angle of the incoming fluid increases in the horizontal direction,for reasons similar to the flow rate.The results can explain theclogging mechanism of geothermal sandstone recharge to some extent,and provide experimental evidence for the numerical simulation of particles depositions in porous media.