The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
James L White - One of the best experts on this subject based on the ideXlab platform.
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Simulation of Screw pumping characteristics for intermeshing counter-rotating twin Screw Extruders
Polymer Engineering and Science, 2011Co-Authors: Qibo Jiang, Jinhai Yang, James L WhiteAbstract:Intermeshing counter-rotating twin Screw Extruders play an important role in polymer processing, espe- cially for the extrusion of profiles and pipe, largely from polyvinyl chloride. There has been little effort on flow modeling of these machines and most of this has involved representing the machine as a ‘‘leaky’’ positive displacement pump and estimating leakages. In recent years, M.H. Hong and the authors have developed more general methods of simulation of flow in this machine and both applied and experimentally verified it for a few designs. Here we extend these efforts to a broader range of Screw designs, especially with deeper Screw channels where transverse shearing induced by the flights is important. Calculations are done for iso- thermal power law fluids. The results are compared with experiment. POLYM. ENG. SCI., 51:37–42, 2011. ª 2010 Society of Plastics Engineers
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a global model for closely intermeshing counter rotating twin Screw Extruders with flood feeding
International Polymer Processing, 2010Co-Authors: Q Jiang, James L White, J YangAbstract:Abstract A composite model has been developed to simulate the extrusion process for intermeshing counter-rotating twin-Screw Extruders. An experimentally based melting model, solids conveying model, and new improved metering model, were combined to develop this formulation. The procedure for global design of a flood feed intermeshing counter-rotating twin Screw extruder is presented. Illustrative calculations are made for polyvinyl chloride and high density polyethylene in this type of machines with different Screw designs. Computations are made for axial variation of the fill factor, pressure, temperature and melting profiles. Simulations were found to match with experimental results well. The model was also applied to scale-up.
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a comparative study of dispersing a polyamide 6 into a polypropylene melt in a buss kneader continuous mixer and modular intermeshing corotating and counter rotating twin Screw Extruders
Polymer Engineering and Science, 2008Co-Authors: K Shon, Sug Hun Bumm, James L WhiteAbstract:We have made a study of the development of phase morphology of an immiscible blend(75/25)(polypropylene–polyamide-6) for different types of continuous mixers including (i) Buss Kneader, (ii and iii) modular intermeshing corotating and counter-rotating twin Screw Extruders, and (iv) NEX-T Kobelco Continuous Mixer. Comparisons are made using different Screw configurations for each machine. Generally, in comparison of the different machines, the intermeshing counter-rotating twin Screw extruder produced the finest dispersed morphology. Using a droplet breakup kinetic model, we interpreted the blend dispersed phase droplet breakdown rate and coalescence rate. In comparison with our earlier study of the continuous mixing of agglomerates of CaCO3 particles the polymer droplet breakup rate was smaller than that of the particle agglomerates and the coalescence rates of droplets were many times greater than the particle reagglomerates rates. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
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development of a global computer software for modular self wiping corotating twin Screw Extruders
Polymer-plastics Technology and Engineering, 2001Co-Authors: James L White, Byongjun Kim, Santosh Bawiskar, Jong Min KeumAbstract:An analysis software for intermeshing modular corotating twin Screw Extruders was developed. A global computation model was incorporated in analysis software. The development of the composite model simulation of solids conveying, melting, and melt flow in a modular corotating twin Screw extruder is described. We discuss the applications of simulation which predict axial fill factor, pressure, temperature, torque, power consumption, specific energy consumption, and average residence time. Design analyses for modular corotating twin Screw Extruders with multiple ports are presented for the various processing conditions. The results are compared for different size of machines. These computation results can assist the process-designing engineer in the optimization of an extruder design and operation parameters for various usage of machine.
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melting model for modular self wiping co rotating twin Screw Extruders
Polymer Engineering and Science, 1998Co-Authors: Santosh Bawiskar, James L WhiteAbstract:A model for the melting process in a self wiping co-rotating twin Screw extruder is described. Self-wiping co-rotating twin Screw Extruders are modular and starve fed. This leads to melting mechanisms that are different from single Screw Extruders. The melting process in the modular Screw configurations generally occurs in specialized sections such as kneading disk blocks. The model, based on our previous experimental observations, considers the formation of two stratified layers of melt in contact with the hot barrel and solid pellets in contact with the relatively colder Screw. In the kneading disk blocks, a part of the solid bed is blocked because of the relative stagger between successive disks. The model predicts both the location of melting and melting lengths in a Screw configuration. Calculations for individual Screw elements and kneading disc elements are presented first. Melting in a modular configuration of these elements is then considered. The effect of operating variables such as mass flow rate and Screw speed on melting is then studied. The model is put in a dimensionless form and the effect of various dimensionless groups is discussed. We make a comparison to the experiment and agreement is good.
Johannes Khinast - One of the best experts on this subject based on the ideXlab platform.
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analysis of flow and mixing in Screw elements of corotating twin Screw Extruders via sph
Aiche Journal, 2017Co-Authors: Andreas Eitzlmayr, Josip Matic, Johannes KhinastAbstract:Due to its meshless nature, the smoothed particle hydrodynamics method (SPH) provides high potential for the simulation of free-surface flows and mixing in complex geometries. We used SPH to analyze the flow inside five typical Screw elements of corotating twin-Screw Extruders, two conveying elements, two kneading elements and a mixing element. Our results show conveying capabilities, pressure generation and power input for various operation states, completely and partially filled. We conducted a detailed mixing analysis based on tracer particles, which yielded the time evolution of the intensity of segregation for different tracers. From that, we determined exponential mixing rates, which describe the relative decrease of the intensity of segregation per Screw revolution and characterize the mixing performance in different operation states. This provides valuable input information for simplified models of Extruders, which are relevant to industrial applications and can significantly contribute to the efficient design, optimization and scale-up of Extruders. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2451–2463, 2017
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co rotating twin Screw Extruders detailed analysis of conveying elements based on smoothed particle hydrodynamics part 2 mixing
Chemical Engineering Science, 2015Co-Authors: Andreas Eitzlmayr, Johannes KhinastAbstract:Abstract Due to the complex geometry of the rotating Screws and, typically, free surface flows in partially filled Screw sections, first principles simulations of the flow in co-rotating intermeshing twin-Screw Extruders using the well-established, mesh-based CFD (computational fluid dynamics) approaches are highly challenging. These issues can be resolved via the smoothed particle hydrodynamics (SPH) method thanks to its meshless nature and the inherent capability to simulate free surface flows. In our previous work, we developed a novel method for modeling the boundary conditions with complex wall geometries, under which SPH could be efficiently applied to complex surfaces of typical Screw geometries of Extruders. In this work, we employed SPH and our boundary method to study the flow in a conveying element in detail. To address unresolved clearances, we developed a new model that is coupled to SPH and can correctly account for the flow through unresolved clearances. A validation of our approach using CFD data from the literature for a completely filled conveying element indicated excellent agreement. Consequently, we studied the flow in a partially filled conveying element and obtained results for the flow rate, the power input and the axial force with variable filling ratio. A detailed analysis of the corresponding mixing phenomena is presented in Part 2. Our results show that the proposed method is a comprehensive approach to study the flow in different types of Screw elements in detail, providing an excellent basis for further development of simplified models of entire extrusion processes.
Guohua Hu - One of the best experts on this subject based on the ideXlab platform.
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assessing local residence time distributions in Screw Extruders through a new in line measurement instrument
Polymer Engineering and Science, 2006Co-Authors: Xianming Zhang, Z Xu, Lianfang Feng, Xiaobo Song, Guohua HuAbstract:This work aimed at developing a new instrument to measure in real time the residence time distribution (RTD) in Screw Extruders. The instrument followed the same principle as the one reported in the literature but possessed several important advantages. For example, the detection system had two probes that allowed to simultaneously measure RTDs at any two different locations of an extruder, thus providing the possibility of calculating the local RTD between them by a deconvolution method based on a statistical theory for the RTD. Its performance was evaluated on a corotating twin-Screw extruder using anthracene as tracer and polystyrene as flowing material. The effects of various process parameters such as feed rate and Screw speed on the RTDs were investigated. The emphasis was placed, however, on the effect of the staggering angle of kneading discs on local RTDs both in the kneading zone itself and its neighboring upstream and downstream Screw zones. This work is in support of an ongoing project on the simulation of flow in corotating twin-Screw Extruders. POLYM. ENG. SCI., 46:510–519, 2006. © 2006 Society of Plastics Engineers.
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one line measurement of the residence time distribution in Screw Extruders
Polymer Engineering and Science, 1999Co-Authors: Guohua Hu, Ilham Kadri, Claude PicotAbstract:A fluorescence monitoring device was constructed to measure in real time the residence time distribution (RTD) function in Screw Extruders. Its centerpiece was an optical fiber probe capable of transmitting optical excitation energy to the processed flow stream and detecting the subsequent fluorescence emission. The source of fluorescence emission was an anthracene-bearing substance that was injected to the flow stream as a pulse (tracer) in very small amounts. This device was validated against an off-line ultraviolet spectrophotometer and self-checked as well. In addition to its great sensitivity to fluorescence emission and ease of implementation on an extrusion line, this device could be used to monitor in real time subtle variations of an extrusion operation. The influence of the nature of anthracene-bearing compounds on the measured distribution and the effects of processing parameters on the RTD function were also investigated.
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residence time distribution in Screw Extruders
Aiche Journal, 1993Co-Authors: Liqin Chen, Guohua HuAbstract:A companion article (Chen and Hu, 1993a) discussed a statistical theory that for a system consisting of two closed subsystems, the residence time density (RTD) functions of the two subsystems will be statistically independent, if a two-dimensional perfect mixing exists at the subsystem boundary. In this case, the overall RTD function is related to that for individual subsystems through the convolution integral. This theory has been validated experimentally using two die-Screw combinations. Based on this theory, a predictive RTD model for an intermeshing counterrotating twin-Screw extruder has been developed. The Screw in the longitudincl direction has been treated as C-chambers in series. The overall RTD of leakage flows has been calculated from the RTDs of these individual chambers and then converted into the RTD of the extruder. The predicted RTD has been tested against experimental results with success.
J. L. White - One of the best experts on this subject based on the ideXlab platform.
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Comparison Studies of Anionic Polymerization of Caprolactam in Different Twin Screw Extruders
International Polymer Processing, 2001Co-Authors: J. L. WhiteAbstract:Abstract There is a study on the comparison of twin Screw Extruders and a batch mixer in the polymerization of caproiactam. A sodium metal initiator and 4–4'-diphenylmethane diisocyanate (MDI) as the activator were used. Our attention is given to (i) a modular intermeshing co-rotating twin Screw extruder, (ii) a modular intermeshing counter-rotating twin Screw extruder and (Hi) a modular tangential counter-rotating twin Screw extruder. We consider the variables of Screw configuration, temperature profile, Screw speed, and throughput on polymer characteristics. It was found that the conversion of twin Screw Extruders with proper mixing segments is much higher than the internal mixer at low mixing times. This was seen as higher conversion in twin Screw Extruders than an internal mixer for the same mean residence time considered.
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a comparative study of residence time distributions in a kneader continuous mixer and modular intermeshing co rotating and counter rotating twin Screw Extruders
International Polymer Processing, 1999Co-Authors: K Shon, D Chang, J. L. WhiteAbstract:Abstract Residence time distributions were measured for a Buss Kneader, Kobelco Nex-T continuous mixer as well as intermeshing co-rotating and counter-rotating twin Screw Extruders using polypropylene with aluminum flakes as a marker. Various modular Screw configurations, Screw speeds and feed rates were considered. Increasing feed rate and increasing Screw speed the mean residence to shorter values and narrows the residence time distribution. Generally, in comparison of the different machines, the intermeshing counter-rotating twin Screw extruder has the shortest mean residence time and narrowest distribution of residence times, while the Buss Kneader has the longest mean residence time and broadest residence time distribution.
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fluid mechanics of intermeshing counter rotating twin Screw Extruders
International Polymer Processing, 1998Co-Authors: M H Hong, J. L. WhiteAbstract:Abstract A simulation is presented of the flow and pumping behavior of an intermeshing counter-rotating twin Screw extruder. The problem of incorporating the positive displacement characteristics of moving machine parts in a cylindrical coordinate Flow Analysis Network (FAN) analysis is presented. Screw pumping characteristic curves were determined for various elements of the Leistritz GG modular counter-rotating twin Screw extruder for a Newtonian fluid. We discuss the analysis of composite modular counter-rotating twin Screw Extruders using these Screw pumping characteristics.
Philippe Tanguy - One of the best experts on this subject based on the ideXlab platform.
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adaptive finite element simulations of fluid flow in twin Screw Extruders
Computers & Chemical Engineering, 2003Co-Authors: Francois Bertrand, F Thibault, L Delamare, Philippe TanguyAbstract:Abstract The objective of this work 1 is to present a new strategy for the transient simulation of fluid flow in geometries involving moving parts and small gaps. It is based upon a fictitious domain method and a mesh refinement technique that relies upon one single reference mesh. With this technique, at each time iteration, the reference mesh may be adapted locally according for instance to the position of the gaps in the computational domain. The method will be discussed in detail and applied to the two-dimensional (2D) simulation of fluid flow in twin-Screw Extruders where one of the key issues is the ability to predict accurately the shear rates in the gaps formed by the rotating Screws.
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Recent progress on the modeling of complex flows in twin-Screw extrusion
Computational Fluid and Solid Mechanics 2003, 2003Co-Authors: Florence Bertrand, R. Giguère, Philippe TanguyAbstract:This work aims at extending to the three-dimensional case a numerical strategy that we have developed in 2D for the transient simulation of fluid flow in twin-Screw Extruders. It consists of combining a fictitious domain method with a mesh refinement technique that relies upon one single reference mesh. The numerical strategy is described and results are presented.
