Experimental study on hydrodynamics of ionic liquids systems in falling film evaporator

Wang, Junnan; Hu, Zongyuan; Dong, Haifeng; Zeng, Shaojuan; Bai, Lu; Zhang, Xiangping; Wang, Yufei

doi:10.1016/j.cep.2021.108701

Cited by 3 publications

(3 citation statements)

References 47 publications

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“…Gentle partial evaporation of the product medium is decisive for product quality, and falling film evaporators are used for this purpose, especially in industrial processes like food production and the evaporation of sucrose solutions [1,2], milk, and fruit juices [3][4][5][6][7][8]. Other applications include solvent separation from oligomers or polymers [9][10][11], separation of petrochemical naphtha [12], and dewatering of ionic liquids [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

2022

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Falling film evaporation processes involve high fluid velocities with continuous variations in local film thickness, fluid composition, and viscosity. This contribution presents a parallel and complementary film thickness and concentration mapping distribution in falling films using a non-invasive fluorescence and near-infrared imaging technique. The experiments were performed with a mixture of glycerol/water with a mass fraction from 0 to 0.65 gglycgtotal−1 and operating ranges similar to evaporation processes. The measurement system was designed by integrating two optical measurement methods for experimental image analysis. The film thickness was evaluated using a VIS camera and high-power LEDs at 470 nm. The local glycerol concentration gglycgtotal−1 was determined using a NIR camera and high-power LEDs at 1050, 1300, 1450 and 1550 nm. A multiwavelength analysis with all NIR wavelengths was implemented with a better correlation for falling films at low flow velocity. The results show an improvement in the analysis of falling films with high flow velocities up to almost 500 mm/s by using only the 1450 nm wavelength and the fluorescence measurement. Simultaneous imaging analysis of film thickness and concentration in falling films provides further insight into understanding mass and heat transport and thus supports the optimization of falling film evaporators.

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Section: Introductionmentioning

confidence: 99%

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

2022

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“…Eichinger et al [20] studied that the R290 film flow inside a vertical round tube, and showed the groove structure improves the wetting behavior and heat transfer. Wang et al [21] measured the film thickness on the vertical plate by the confocal chromatic technique, a film thickness correlation was proposed for the ionic liquids.Li et al [22] numerically studied the film flow outside the vertical tube, and found the ripple surface structure hinders the film spreading, which results in smaller velocity and greater film thickness compared with the smooth tube. Jourdan et al [23] investigated the wettability and film thickness on the cooling tower packing by the fluorescence method.…”

Section: Introductionmentioning

confidence: 99%

“…The working fluids studied in the existing literature are mainly concentrated in pure water [5][6][7][8]10,11,13,19,23,25], seawater [3], oil sewage [15,16], LiBr solution [17], freon refrigerant [9,20,22], ethylene glycol aqueous solution [14], potassium formate aqueous solution [24], ionic fluid [21,22]. For the cryogenic liquid, Pavlenko et al [26] measured the film flow of cryogenic liquid nitrogen on the surfaces with complex geometry, and found the microstructure has a significant influence on the film spreading progress.…”

Section: Introductionmentioning

confidence: 99%

Falling Film Flow and Heat Transfer of Cryogenic Liquid Oxygen on Different Structural Surfaces

et al. 2022

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The accurate prediction of the falling film characteristics of cryogenic liquids is necessary to ensure good evaporation performance, due to their special physical properties. In this study, the film flow and heat transfer characteristics on four different structures were investigated, and the performance of the cryogenic liquid oxygen was compared with other fluids with higher temperatures, which demonstrates the influence of structures and liquid mediums. The VOF model was used to capture the film surface in the simulation model. The results show that for the four structures, liquids with higher kinematic viscosity tend to have greater film thickness, and the sensible heat transfer coefficients are inversely related to the nominal thermal resistance of falling film flow. Both on the smooth plate and the corrugated plate, the film wettability depends on the kinematic viscosity, rather than the dynamic viscosity, and the effect of kinematic viscosity is greater than that of surface tension. Both the local heat transfer coefficient and its fluctuation amplitude decrease gradually along the flow direction on the triangular corrugated plate, and the vortices are easier to produce at the wall troughs when the film viscosity is higher. At the bottom of the horizontal tube, the increases in local film thickness of the liquid oxygen are less than those of the water and the seawater. More liquid tends to accumulate at the bottom of the round tube, while it easily detaches from the film surface of the elliptical tube. For the horizontal tubes, the local heat transfer coefficients decrease rapidly when θ = 0–5°, and increase sharply at θ = 175–180°.

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A Review of Falling Film Evaporation Under Different Surface Structures and External Disturbances

Wan,

2025

J Enh Heat Transf

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Falling film evaporation has been proposed as a promising alternative to traditional pool boiling heat exchangers due to advantages such as lower pressure drop, heat transfer improvement, and refrigerant charge reduction. This paper provides a comprehensive review of recent advancements in falling film flow and heat transfer characteristics, specifically focusing on various surface structures, including smooth plates, corrugated plates, vertical tubes, and horizontal tubes. In the case of film flow on plates, this review highlights key aspects such as film thickness, film wave evolution, wettability, and heat transfer properties. The study further reviews findings on film flow along both the inner and outer surfaces of vertical tubes, as well as horizontal round tubes and non-round tubes. The enhanced tubes can be divided into tubes machined with fins and coated with material. Noteworthy findings regarding flow pattern transitions, film thickness, and heat transfer characteristics on horizontal tubes are comprehensively outlined. Furthermore, the impact of external disturbances on film flow and heat transfer is also reviewed. Finally, several challenges and prospective directions for future research are established.

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Experimental study on hydrodynamics of ionic liquids systems in falling film evaporator

Cited by 3 publications

References 47 publications

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

Falling Film Flow and Heat Transfer of Cryogenic Liquid Oxygen on Different Structural Surfaces

A Review of Falling Film Evaporation Under Different Surface Structures and External Disturbances

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