The performance of laminar Taylor-Couette flow with different developed procedures is studied by the way of computational fluid dynamics (CFD) in steady state. In order to gain a group of developed procedure in CFD, a set of convergent solutions are used as the initial value of next boundary condition, and the new set of convergent solutions are regarded as developing from the previous steady state. Three groups of developed procedures are gained from the rotating speed series of inner cylinder, respectively from the gradual increase procedure (GIP), the gradual decrease procedure (GDP) and the sudden increase procedure (SIP). It is proved that the convergent solutions of fluid control equations are different when they are solved from laminar state with the same boundary condition, the same fluid property, the same mesh grid in CFD and the same business software except that the flow states have developed from the procedures of GDP, GIP and SIP. It is shown that the developed procedure could leave behind some information in the performance of the flow. In other words, the flow between concentric rotating cylinders has somewhat memory for the procedure of its history
The spiral membrane separator is a novel module proposed for reducing the concentration polarization and membrane fouling of membrane separation process. This membrane separation process benefits from dean vortices produced by centrifugal instability in enhancing fluid mass transfer. A numerical stimulation of this membrane separation is presented and used to analyze the fluid flow characteristics and thoroughly understand the separation mechanism. The numerical model consists of a spiral flow path with rectangular sector. As the simulation with infiltration, the fluid domain of the ceramic membrane tube was as a porous medium domain. The standard momentum equation, added with the momentum equation source term which composed of the viscosity loss term and the inertia loss term, are figured out through the experimental characterization. In the simulation of spiral membrane separation, the Dean secondary flow structure is identified and found to enhance fluid mass transfer and to increase the permeate flux. The critical unstable state of spiral membrane separation is accordingly De=246 without the flow permeation and De=863 with the permeation, where Dean vortices cause collisions and the mixing of fluid particles. Then in the case of permeation, the fluid in separator at De=1232 is numerically simulated to show that the higher flow velocity and a large fluctuating trend of wall shear stress near the membrane surface (inside), which mainly contributed to alleviate concentration polarization and membrane fouling.
China is a large country in the production and use of pesticides, and the production and use of pesticides are among the highest in the world. According to statistics, the ratio of wastewater from pesticide production to wastewater discharged is about 1:100. Arbitrary discharge of a large amount of pesticide wastewater has caused serious environmental problems. The main way of pesticide wastewater treatment is to optimize emission reduction and control emissions. At present, treatment is the main way. There are many kinds of pesticide wastewater, which need targeted treatment, greatly increasing the difficulty of treatment. This paper takes the salty waste phenol wastewater discharged from a pesticide factory as the carrier, through basic physical property analysis, thermal property detection, crystallization kinetics research, basic small test, pilot scale amplification, research and development for the evaporation of this wastewater, crystallization processing equipment. In order to optimize the process route, it is preferable to use MVR compressor technology in comparison with multi-effects. Under the conditions of evaporation temperature 75°C to 90°C, compare the parameters of compressor power, cooling water volume, total energy consumption of evaporation crystallization device, total area, etc., and determine the evaporation temperature to be 90°C. In order to improve the energy utilization rate, the heat such as condensed water, crystal slurry output, and mother liquor reflux is rationally utilized. The multi-stage plate preheater and plate evaporator are used in the equipment design. The separator and condensed water vapor-liquid separation device adopt the patented structure to improve the operation efficiency.
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