Aluminum hose and aluminum hose production line research New technology After nearly a century of experimental research and theoretical exploration, today's aluminum hose technology has entered a period of rapid development, and accumulated a lot of design experience and correlation can be used to analyze and predict the hybrid system. However, due to the diversity of fluid mixing system and the complexity of material rheological characteristics, the selection and design of mixing equipment still mainly rely on experience and experiment, and it is difficult to predict its advantages and disadvantages with theory. For energy consumption and production cost, it can only be distinguished by comparing on a certain scale of production equipment. In addition, the amplification law of stirring equipment is still not enough understanding, lack of theoretical guidance. Therefore, from a more microscopic and essential point of view, using advanced testing methods and computational fluid dynamics methods to obtain the velocity field, temperature field and concentration field in stirring equipment, not only has important economic significance for the optimal design of stirring and mixing equipment, but also has practical theoretical significance for the basic research of amplification and mixing. 1 LDV/PIV measurement technology The accurate measurement of flow velocity in stirring equipment is a complicated work. This is because the flow in the stirring equipment is a three-dimensional and highly unstable turbulence, and the pulsation and random turbulence bring great difficulties to the velocity measurement.

Early methods of velocity measurement, such as pitot tubes, electromagnetic current meters, piezoelectric probes, and hot wire or hot film anemometers, interfered with the flow by plugging probes into the flow field. Since the 1980s, the Laser Doppler Velocimetry (LDV) was used to measure the flow field in the stirred kettle. LDV measurement is carried out at a certain measuring point within a period of time, so the measured velocity is a time-averaged quantitative value. The whole flow field can be obtained by measuring each point in the stirred kettle. However, since these measurements cannot be made at the same time, LDV cannot be used to study unsteady flows. In order to study the time-varying flow, the more advanced Particle Image Velocimetry (PIV) must be adopted, which can see the whole distribution of the flow field instantaneously. The principle is that the stirring equipment is irradiated by a slit laser beam, and two pulses are used to excite the light source, so as to obtain the two-exposure image of the particle in the field, and then the velocity field is calculated from the displacement of the particle during the exposure time. However, the technology development of PIV is still not perfect, and it is still in the early stage of application. At present, it can not measure the turbulence parameters under high speed turbulence well.

Using LDV measurement technology, abundant information such as time-mean velocity field, turbulence intensity field, Reynolds stress field and shear rate field in stirred tank can be accurately obtained, and macro characteristic parameters such as displacement and power consumption can be further calculated. The Computational Fluid Dynamics (CFD) model uses LDV measurements to validate the Computational Fluid Dynamics (CFD) model and to provide the model boundary conditions. In recent years LDV has also been used to measure the stirring characteristics of multilayer paddle, such as displacement and circulation flow. Because the particle tracking method used to measure the displacement of single-layer agitator is not applicable to the multi-layer impeller condition. 2. The CFD simulation technology LDV only provides some important parameters such as the displacement criterion, the distribution of average time velocity and pulsation velocity, etc., but it cannot essentially understand mixing and flow, and cannot change the current situation of relying on experience to amplify. Therefore, it is the development trend of fluid mixing technology to use computational fluid dynamics method to simulate and predict the detailed flow and mixing characteristics of stirring equipment with different geometric sizes and operating conditions. At present, the most widely used numerical simulation of flow in stirring equipment is the steady-state analysis of agitator with the black-box model, that is, the velocity field measured by the experiment on the fictitious surface around the agitator is taken as the boundary condition or the action of the blade on the fluid is taken as the source of the fluid momentum. From the point of view of numerical calculation, the black-box model has the characteristics of simplicity and convenience, and can accurately predict the motion characteristics of agitator under different conditions. However, this method requires the experimental data as the paddle boundary conditions, so it cannot be used for the simulation of multiphase flow system. The most important application of CFD (and the main advantage of CFD technology) is the analysis of flow field, which can clarify the influence of flow field on mixing, suspension and dispersion processes under the conditions of different agitator types, sizes and distance from the bottom, that is, the calculation and visualization of CFD flow and energy dissipation. Thus, the user can intuitively understand the mixing situation in the kettle, help the user to determine the existing problems in the system, guide the user to optimize the design of the agitator, eliminate the dead zone, determine the location of the feeding port, etc.

At present, foreign professional mixing equipment companies have used CFD technology to optimize the geometrical size of agitator and developed the second generation of high-efficiency axial flow agitator. Another major advantage of CFD is the facility size independence of the models. Once they have been verified to describe the stirred reactor process reasonably accurately, they are used to scale up to predict the scaled-up rod and reaction performance. With the development of CFD technology, compressible fluids and some simple inelastic viscous fluids have become possible to simulate in commercial software. At present, the CFD simulation of multiphase flow (especially gas-liquid system) has made great progress, but there is still a considerable distance between it and the practical application. EPT is a non-contact real-time detection and visualization technique for multiphase flow systems. It can measure the flow field of opaque media. EPT works in much the same way as CT, a medical test instrument. A set of 8 to 16 sensors is equidistant attached to the outer wall of the stirred kettle or pipe under test. The sensor is a rectangular stainless steel electrode, which is both a transmitter and a receiver. There are two kinds of materials with different electrical properties (conductivity, capacitance, etc.) in the kettle or pipeline (liquid, gas and solid with different conductivity, liquid and solid), and then under the action of regular electrical pulses, all possible adjacent sensor combination voltage is transmitted back to the computer through the data acquisition unit. The computer records the signals and sequence of all the electrodes and uses an image reconstruction technique to reconstruct the cross-section of the kettle or pipe, producing up to 100 frames per second. If multiple sets of sensors are used for tomography at different heights, the three-dimensional image and solid modeling of the kettle or pipeline can be established with the aid of image reconstruction technology. EPT systems are radiation-free, inexpensive, easy to manufacture, faster than CT and can meet the requirements of industrial real-time processes. But the image resolution is lower than that of CT. EPT can accurately measure the flow zone in the stirred reactor.