Unsal E, Mason G, Ruth D W, Morrow N R
Department of Chemical Engineering, Loughborough University, Loughborough, UK.
J Colloid Interface Sci. 2007 Nov 1;315(1):200-9. doi: 10.1016/j.jcis.2007.06.070. Epub 2007 Jul 3.
A model for co- and counter-current imbibition through independent capillaries has already been developed and experiments conducted to verify the theory [E. Unsal, G. Mason, N.R. Morrow, D.W. Ruth, J. Colloid Interface Sci. 306 (2007) 105]. In this paper, the work is extended to capillaries which are connected laterally and in which cross-flow can take place. The fundamental pore geometry is a rod in an angled round-bottomed slot with a gap between the rod and a capping glass plate. The surfaces of the slot, rod and plate form capillaries and interconnecting passages which have non-axisymmetric cross-sections. Depending on the gap size either (i) a large single meniscus, (ii) two menisci one on each side of the rod, or (iii) three menisci, one between the rod and the glass additional to the ones on each side can be formed. A viscous refined oil was applied to one end of the capillaries and co-current and counter-current spontaneous imbibition experiments were performed. The opposite end was left open to the atmosphere for co-current experiments. When the gap between the rod and the plate was large, the imbibing oil advanced into the tubes with the meniscus in the largest capillary always lagging behind the two menisci in the other two smaller capillaries. For counter-current imbibition experiments the open end was sealed and connected to a sensitive pressure transducer. In some experiments, the oil imbibed into the smaller capillaries and expelled air as a series of bubbles from the end of the largest capillary. In other experiments, the oil was allowed to imbibe part way into the tubes before counter-current imbibition was started. The meniscus curvatures of the capillaries have been calculated using the Mayer and Stowe-Princen method for different cell slot angles and gap sizes using a value of zero for the contact angle. These values have been compared with actual values by measuring the capillary rise in the tubes; agreement was very close. A model for co-current and counter-current imbibition has also been developed. The significance of this model is that some hydraulic/capillary properties are common for both co-current and counter-current imbibition. The experiments give an illustration of behavior expected in a real porous material and verify the importance of the 'perfect cross-flow' modification to the 'bundle of parallel tubes' model.
一个关于通过独立毛细管进行并流和逆流吸渗的模型已经建立，并且已经开展了实验来验证该理论[E. 乌萨尔、G. 梅森、N.R. 莫罗、D.W. 鲁思，《胶体与界面科学杂志》306 (2007) 105]。在本文中，这项工作扩展到了侧向连接且能发生错流的毛细管。基本的孔隙几何形状是一根置于有角度的圆底狭槽中的杆，杆与覆盖玻璃板之间存在间隙。狭槽、杆和板的表面形成了具有非轴对称横截面的毛细管和相互连通的通道。根据间隙大小，要么形成（i）一个大的单一弯月面，（ii）杆两侧各有一个弯月面，要么形成（iii）三个弯月面，除了杆两侧的弯月面外，杆与玻璃之间还有一个弯月面。将一种粘性精制油施加到毛细管的一端，并进行了并流和逆流自发吸渗实验。对于并流实验，另一端向大气开放。当杆与板之间的间隙较大时，吸渗油进入管中，最大毛细管中的弯月面总是落后于另外两个较小毛细管中的两个弯月面。对于逆流吸渗实验，开放端被密封并连接到一个灵敏的压力传感器。在一些实验中，油吸渗到较小的毛细管中，并从最大毛细管的末端以一系列气泡的形式排出空气。在其他实验中，在开始逆流吸渗之前，让油部分吸渗到管中。使用迈耶和斯托 - 普林森方法，针对不同的单元狭槽角度和间隙大小，在接触角取值为零的情况下，计算了毛细管的弯月面曲率。通过测量管中的毛细管上升高度，将这些值与实际值进行了比较；二者吻合得非常紧密。还建立了一个并流和逆流吸渗的模型。该模型的意义在于，一些水力/毛细管特性对于并流和逆流吸渗是共同的。这些实验展示了在实际多孔材料中预期的行为，并验证了对“平行管束”模型进行“完美错流”修正的重要性。
