An Experimental Study On The Deposition Characteristics Of Suspended Particles In Heated Saturated Porous Media

Particle deposition in saturated porous media is widely recognized to occur in both industry and nature,which is an important and significant issue for many applications such as geothermal reinjection,oil exploitation,pollutant purification,soil and water conservation,filtration system and so on,and it's been an important issue in many scientific fields and industrial applications.However,a very few previous studies involved the impact caused by temperature difference between porous media and suspension fluid.Based on the above background,we conducted a series of seepage tests by using self-made porous section in a cylinder with constant heat flux boundary condition along the wall,and a static experiment system was also established,of which the bottom wall of the test section can be heated electrically or the temperature controlled by a refrigeration system.The contents of the thesis include mainly two aspects: experimental results and their analysis.The deposition and transportation characteristics of microparticles suspended in water flowing vertically downwards through a heated porous column were experimentally studied.The amount of deposited particles at the interface and inside porous column and pressure change at difference location at the conditions with and without circumference heating,or the effect of temperature gradient perpendicular to the flow direction were focused in our experiments,in which the porous columns and inlet concentration of suspended fluid were kept the same.In addition,the seepage stability,the tube wall temperature distribution,and the relative permeablities for each section are analyzed.The results show that the relative permeability kt/k0 is obviously different at different heating temperature gradients while having the same original porous media,and inlet concentration of suspensions.The deposition rates both at the entrance interface and inside porous medium increase with an increase of temperature difference,however,the stability of the deposited structure decreases.By using the static experiment system,successive visualizations and balance weighting experiments were carried out for the micro-particle deposition with different temperature boundary condations,and some comparsons were made,for example,the deposited depth and weight with time for different cases in order to clarify the effect of temperature difference.The analysis of test results shows that the factors temperature gradients,as same as particles size,particles concentration and size of porous media had a great impact at shape and mass of the deposition,the proportion of different influence factors may also be different at different experimental conditions,by the way,these influence factors are connected and interacted to each other,the change of one certain factor can change the effect of other factors on the deposition effect.