The membrane filtration device of claim 1 wherein the membrane sheets and all spacers except those in the permeate channels are recessed at least about one inch from the axial end of the wound membrane at each permeate discharge end of the wound membrane sheets. The membrane filtration device of claim 1 comprising a spacer sheet in each permeate channel consisting of a knitted permeate fabric having a hydraulically impervious plastic film laminated to at least one edge thereof. The membrane filtration device of claim 1 wherein the membrane sheets are of the reverse osmosis type.
There are a variety of membranes in use throughout the market which act as processes in treating groundwater, surface water, and wastewater to a level that is acceptable for industries and especially consumption. It is a rapidly growing industry, as a result of the need to combat low quality water sources such as rivers, lakes, wells, streams, and the ocean, in order to provide more alternative methods in supplying healthy, safe, steady, and accessible water to the masses. 1 shows a cut-away view of a typical reverse osmosis spiral wound membrane element 1 of this invention within a cylindrical RO pressure vessel 2. The membrane element 1 is sealed within the pressure vessel 2 with end plates 2a and 2b containing ports for the various feed, concentrate and permeate nozzles and retained in position by ring clamps 10a and 10b.
In 1994, two new arbitrary quadrilateral membrane elements called GQ12 and GQ12M with vertex rotation were proposed by Long and Xu , resulting in more reasonable compatible conditions between adjoining elements and a more simple formulation. The membrane elements are among the simplest elements to develop, which are used for analyzing structures subjected to in-plane forces. The membrane elements are usually used to model the behavior of shear wall, stiffened sheet construction, and membrane action in shells. Some plane elements can be considered as membrane elements, such as the CST element and the four-node isoparametric quadrilateral plane element . In finite element methods, many plate bending elements also have been developed. Bazeley et al. developed the confirming and nonconfirming plate bending elements in 1966.
The high pH cleaning should always be performed first to penetrate and disperse biological or organic foulants. Specialty high pH cleaning chemicals more effectively penetrate heavy organic and biological foulants, making them more effective than commonly used CIP chemicals such as sodium hydroxide. While many choose the lowest cost CIP chemicals, their annual cost will end up being significantly higher because of the higher frequency of cleaning, this incurs more labor costs, chemical costs, and downtime. It’s always best to perform a cleaning study to ensure that membrane performance is fully restored after CIP. The outcome of a membrane cleaning is equally dependent on procedure as it is on the quality of the cleaning chemical. However, an optimal procedure isn’t always possible to implement due to limitations in the design of the Clean-In-Place system.
If the mesh is sufficiently small, then midside nodes may not provide any significant increase in accuracy. The membrane element allows the definition of pressure loads normal to the surface, e.g., to model wind loads on a sail. The convergence of the element for this type of loading is improved if the element is in tension, otherwise the element is free to flap around and convergence difficulties may arise. Temperature dependent, anisotropic material properties can be defined.
Structural and thermal bricks exist so the same model geometry can be used for both the initial steady state heat transfer and subsequent thermal stress computations. 2D Elements are 3 or 4 node elements with only 2 DOF, Y and Z translation, and are normally created in the YZ plane. Common applications include axisymmetric bodies of revolution such as missile radomes, radial seals, etc. and long sections with constant cross sectional area such as a dam. Plane Stress implies no stress normal to the cross section defined – strain is allowed – suitable to model the 2D cross section of a body of revolution.