Residence time in a single screw free helix extruder using a new solution to the biharmonic equation

Campbell, Gregory A.; Bomma, Sirisha; John, Samuel St.; Chempath, Shaji; Hunt, Diana; Taylor, Ross; Powers, David L.; Wetzel, Mark D.

doi:10.1002/pen.25567

Cited by 4 publications

(9 citation statements)

References 36 publications

(40 reference statements)

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“…In general, the multiple peaks from the experiments can also be found in the simulation results for screw rotation. This suggests that the analytical solution using the bi‐harmonic equation developed by Campbell et al quite accurately represents the flow in the rectangular channel 6 . For the four drops‐discs, the chaotic simulation was semiquantitatively representative of the experimental data.…”

Section: Methodsmentioning

confidence: 71%

“…Simulations of the flow in this device can be found from the method developed recently by Campbell et al 6 The difference in this investigation is the utilization of boundary conditions that produce chaos in the extruder. The reader is referred to that paper for complete details of the calculation procedure.…”

Section: Simulating Chaotic Mixing In the Free-helix Extrudermentioning

confidence: 99%

“…This article will focus on chaotic mixing experiments carried out in a novel “free‐helix” extruder that had the flight‐helix as a separate element of the extruder screw which was operated to produce deterministic chaotic mixing. A new technique was developed to introduce the tracer that better correlates with the predictions of a recently published three‐dimensional (3D) model based on a solution of the biharmonic equation to simulate the flow of Newtonian viscous fluids in the extruder 6 . The device used in this research had what is referred to as a deep channel with an aspect ratio H / W = 0.85.…”

Section: Introductionmentioning

confidence: 99%

“…The free‐helix extruder is a device in which we can obtain 3D chaotic mixing by making the top (barrel), and bottom (core) walls move alternately (as viewed from a frame of reference attached to the helix). Simulations of the flow in this device can be found from the method developed recently by Campbell et al 6 The difference in this investigation is the utilization of boundary conditions that produce chaos in the extruder. The reader is referred to that paper for complete details of the calculation procedure.…”

Section: Introductionmentioning

confidence: 99%

“…A new technique was developed to introduce the tracer that better correlates with the predictions of a recently published three-dimensional (3D) model based on a solution of the biharmonic equation to simulate the flow of Newtonian viscous fluids in the extruder. 6 The device used in this research had what is referred to as a deep channel with an aspect ratio H/W = 0.85. The modeling of single-screw extruder flow is next reviewed to set the foundations of the chaotic mixing analysis.…”

Section: Introductionmentioning

confidence: 99%

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Chaotic mixing in a free‐helix extruder using a new solution to the biharmonic equation

Campbell

Taylor

Wetzel³

et al. 2022

AIChE Journal

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A recently published approach for modeling the cross flow in an extruder channel using a new solution to the biharmonic equation is utilized in a study of chaotic mixing in a free‐helix single‐screw extruder. This novel extruder was designed and constructed with the screw flight, also referred to as the helix, detached from the screw core. The flight‐helix had straight sides that more closely emulated rectangular channel theory than the nominal sloped sides of a conventional single screw channel. Each of the screw elements could be rotated independently to obtain chaotic motion in the screw channel. Using the new extruder, experimental evidence for the increased mixing of a dye, for both a Dirac and droplet input, with a chaotic flow field relative to the traditional residence time distribution is presented. These experimental results are compared using the new biharmonic equation‐based model. Comparing the experimental chaotic mixing with theoretical calculations was facilitated by a recently published technique for accurately placing the dye in the extruder channel. Because of the ability to periodically rotate only the flight/helix, the chaotic mixing results are minimally confounded by the existence of Moffatt eddies.

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Section: Methodsmentioning

confidence: 71%

Section: Simulating Chaotic Mixing In the Free-helix Extrudermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Chaotic mixing in a free‐helix extruder using a new solution to the biharmonic equation

Campbell

Taylor

Wetzel³

et al. 2022

AIChE Journal

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A new 2.5‐D twin screw extruder melting model with comparisons to data

Campbell,

Wetzel,

Andersen

et al. 2023

Polymer Engineering & Sci

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Many polymers are processed and compounded in co‐rotating, fully intermeshing twin screw extruders. A typical compounding process consists of multiple unit operations including feed introduction, solids transport, transitioning from the conveying zone to the kneading block melting zone, melting, a downstream feed zone, a mixing zone, a devolatilization region, and a pressure generating discharge section. This paper will focus on the kneading block melting zone which typically includes a reverse pitch element so the kneaders remain full. Mechanisms for flow and energy input to pellets in kneading elements, including friction heating, pellet compression, energy diffusion, and viscous dissipation to form a melt phase: followed by viscous dissipation in a solid pellet/melt slurry, and heat transfer; are developed and implemented in a novel melting model. The model is validated with extrusion measurements and visualizations using low density polyethylene (LDPE). The predictions of the model are also compared with a classical set of experiments using high density polyethylene (HDPE). This paper describes the physics and engineering concepts that the authors feel are inherent in the melting section of the twin screw extruder where a large pressure peak is calculated using the friction and compression of the polymer pellets. The modeled increase in pellet bulk/surface temperature is due to the inclusion of four energy sources, pellet compression, thermal diffusion, friction energy dissipation, and viscous energy dissipation. This combined thermal dynamics based melting model results in a novel melting protocol. The melting mechanisms are coupled to flow regimes in the kneading blocks as melting progresses. The effects of throughput, Q, and screw rotation speed, N, are also examined.Highlights Novel 2.5D melting model for corotating, intermeshing twin‐screw extruders. Energy for melting; friction, deformation, diffusion, and viscous dissipation. The model helps elucidate mechanisms during melting in a twin‐screw extruder.

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Melt Homogenization

Andersen,

Campbell

2022

Extruder Processing

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Residence time in a single screw free helix extruder using a new solution to the biharmonic equation

Cited by 4 publications

References 36 publications

Chaotic mixing in a free‐helix extruder using a new solution to the biharmonic equation

Chaotic mixing in a free‐helix extruder using a new solution to the biharmonic equation

A new 2.5‐D twin screw extruder melting model with comparisons to data

Melt Homogenization

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