Flow cells are used for a variety of column experiments. They are used most often for column leaching experiments. Such studies are designed to determine rates of movement of water and chemicals (i.e. nutrients, tracers, organics, metals etc.) through soil, and to determine physical and chemical parameters.
Flow cells are also used to study the hydraulic properties of soils, such as the saturated hydraulic conductivity, the unsaturated hydraulic conductivity, and soil water retention.
By using SMS flow cells all of these hydraulic properties (the saturated hydraulic conductivity, the unsaturated hydraulic conductivity, and soil water retention) can be determined on the same soil core. Column tensiometers are recommended, for determining the unsaturated hydraulic conductivity. Small column tensiometers, with or without pressure transducers, are available from SMS.
A flow cell is usually made of cast acrylic, but aluminum and stainless steel flow cells can be made on special order. A flow cell consists of a tube, which holds the soil or other porous medium, and two removable end-plate assemblies, one mounted on each end of the tube. Each end-plate assembly has one access port in its center. Additional access port can be ordered for the-endplate assemblies, as well as for the acrylic or metal tubes. Borosilicate glass tubes are also available. The tube and the top and bottom end-plate assemblies are held together with 3 rods.
Each end-plate assembly consists of two parts: a round doughnut shaped part containing an o-ring slides over the end of the column, and a flat round plate which holds a perforated aluminum support disc. There is a gasket between the two plates, as well as a porous nylon membrane (bubbling pressure 30 mbar) or a membrane filter (bubbling pressure 600 mbar). When needed, the membranes can easily be replaced. The round doughnut shaped part of the end plate assembly for 5.25 inch OD flow cells is made of aluminum.
Flow cells come in nine standard tube diameters: 1.5, 2.0, 2.25, 2.5, 3.0, 3.25, 3.5, 4.0, and 5.25 inches outside diameter. The inside diameters are 0.5 inches less than the outside diameters. For different diameters (including metric sizes) contact SMS. Flow cells can be made in nearly every length.
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