Numerical simulation of the behavior of high‐viscosity fluids falling film flow down the vertical wavy wall

Chen, Shichang; Ma, J.P.; Zhang, Xianming

doi:10.1002/apj.2057

Cited by 6 publications

(3 citation statements)

References 29 publications

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“…Such technique overcomes the limitations of melt polycondensation due to the rate of glycol removal from high‐viscosity molten polymers, can produce PET with a high IV of 1.0 dL g −1 . When the IV of PET increases from 0.65 to 1.0 dL g −1 in this technique, the strength of the corresponding filament increases about twice and it has become particularly useful in the manufacture of PET industrial yarns …”

Section: Introductionmentioning

confidence: 99%

Continuous post‐polycondensation of high‐viscosity poly(ethylene terephthalate) in the molten state

Wang

Chen

Guang

et al. 2019

J of Applied Polymer Sci

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Time‐resolved rheometry and size exclusion chromatography system [advanced polymer chromatography (APC)‐multi‐angle laser light scattering (MALLS)‐refractive index detector (RID)] were employed to investigate post‐polycondensation process of nonstirred high‐viscosity poly(ethylene terephthalate) (PET) of molten film forming by high‐flow inert gas sweeping at atmospheric pressure. In view of chemical reaction kinetics together with mass transfer to adjust reactive parameters, including moisture content of the sample, temperature, concentration of the active groups, residence time, and mass transfer factor, this work aims to distinguish the different reactions in reprocessing of high‐viscosity PET. Results indicated that hydrolysis is observed initially before thermal degradation and polycondensation reactions on remelting process. Promotion of thermal degradation is stronger than polycondensation with the increase in temperature. Fiber‐grade PET exhibits polycondensation as the dominant reaction at 275 °C in a reasonable reaction time, which leads to the increase of average molecular weight and the phenomenon of double distribution proved by APC‐MALLS‐RID system. However, the average molecular weight of industrial yarn‐grade PET is very difficult to improve when the thermal degradation reaction is not effectively inhibited. Importantly, the experimental study of the interfacial mass‐transfer area and mass‐transfer intensification demonstrated that mass transfer is the rate‐determining factor for the overall post‐polycondensation of high‐viscosity melt. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47484.

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Section: Introductionmentioning

confidence: 99%

Continuous post‐polycondensation of high‐viscosity poly(ethylene terephthalate) in the molten state

Wang

Chen

Guang

et al. 2019

J of Applied Polymer Sci

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“…Furthermore, the sinusoidal corrugation and a novel design consisting of isolated semicircular bumps distanced by the wavelength of the surface waves were verified to have better heat and mass transfer compared with the flat wall 33 . Chen et al 34 numerically studied the film flow on the vertical wave plate with high‐viscosity fluids. They found that the flow behavior of high‐viscosity fluids is partly different from that of low‐viscosity fluids.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the falling film wettability and heat transfer on the inclined plates with different corrugated structures

Wan

2021

Asia-Pacific J Chem Eng

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In this study, 2D and 3D models of corrugated plates using the volume of fluid (VOF) model were set up to simulate the influence of corrugated structure on the wettability and heat transfer. The results show that compared with the triangular corrugation, the rectangular corrugation has a slower growth rate of wetting ratio (WR) as the Weber number (We) increases under the same corrugation length Le and corrugation depth De. The average WR of the triangular corrugation is 2.8% less than that of the smooth plate. For the triangular corrugation, the higher Le contributes to improving wettability, but the average heat transfer coefficient havg first decreases to the minimum at Le = 5 mm and then increases 8% to 9% to a steady value until Le = 8 mm. WR decreases with De at We ≤ 0.76. A WR correlation considering the corrugation steepness St (St = De/Le) and a critical Re correlation corresponding to the minimum wetting rate were fitted for the liquid oxygen. As the inclination angle ϕ increases, the average film thickness decreases and havg increases until ϕ = 75°, while the variation rate slows down afterwards. At Re = 1200, havg has a decreasing trend at St ≤ 0.13, increases at St ≥ 0.14 and reaches a plateau after St = 0.24 as St increases. It increases by 30.6%, 47.4%, and 44.4% for the inclination angle ϕ = 30°, 60°, 90° cases from St = 0.14 to 0.24. The enhancement is caused by the vortices existing at St ≥ 0.14.

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“…A wide range of high-viscosity fluids (1.5–210 Pa·s) was employed by Xi et al, who considered the falling film flow in a grid falling film tower and suggested that the falling film form can be used in polymer melt devolatilization and polymer reaction engineering. Chen et al , designed wave structures of different sizes on vertical tubes to drive the lateral disturbance of high-viscosity fluids (0.92–623 Pa·s) in the falling film flow, proving that the high-viscosity fluids flow on the wave structure not only has a high film-forming effect but also significantly improves the sufficient surface renewal frequency, which is more conducive to heat and mass transfer. In brief, the patterns of falling film flow in the cases of high-viscosity fluids are not as rich as the patterns of low-viscosity fluids; unique and valuable flow characteristics still exist that deserve further study.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation and Experimental Verification of the Film-Forming Behavior of Falling Film Flow Down Clamped Channels with High-Viscosity Fluid

Wang

Chen

Lin

et al. 2020

Ind. Eng. Chem. Res.

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The film-forming behavior of falling film flow with a high-viscosity fluid in clamped channels was investigated numerically and experimentally. The present work puts forward and deeply investigates a new method of falling film flow in the field of industrial engineering. The new findings from computational fluid dynamics (CFD) agree well with the experimental results. Flow patterns can be observed and divided into three flow patterns: columnar flow, partial curtain flow, and curtain flow. In terms of different flow patterns, the evolution of the liquid film along the direction of gravity was diversified, mainly including coalescence, break-up, shrinkage, and expansion. In addition, the shape of the free surface depended mainly on the physical properties of the fluid, the geometrical structure of the channel, and the spray density. The convex ratio k of the liquid film varied between 0 and 1.2, and such a wide range indicated that the free surface of the liquid film would be visually bent, resulting in a large area for the gas–liquid interface and a very high level of the film-forming efficiency. More interestingly, the desired shape of the liquid film was obtained by regulating the structural factors r and d. Based on the above conclusions, the method concerning falling film flow down clamped channels could be beneficial to enhance the heat and mass transfer in the process intensification of industrial engineering.

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Numerical simulation of the behavior of high‐viscosity fluids falling film flow down the vertical wavy wall

Cited by 6 publications

References 29 publications

Continuous post‐polycondensation of high‐viscosity poly(ethylene terephthalate) in the molten state

Continuous post‐polycondensation of high‐viscosity poly(ethylene terephthalate) in the molten state

Numerical study of the falling film wettability and heat transfer on the inclined plates with different corrugated structures

Numerical Simulation and Experimental Verification of the Film-Forming Behavior of Falling Film Flow Down Clamped Channels with High-Viscosity Fluid

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