Hydrodynamics numerical simulation of a vertical falling film evaporator for ionic liquid systems

Hu, Zongyuan; Wang, Junnan; Dong, Haifeng; Hussain, Shahid; Zeng, Shaojuan; Nie, Yi; Zhang, Xiangping; Zhang, Suojiang

doi:10.1016/j.ces.2021.116563

Cited by 11 publications

(3 citation statements)

References 49 publications

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“…In this work we used a numerical simulation method. The mathematical model of the two phase vaporliquid flow with the interphase surface for the tube space is semi-empirical and describes changes in absolute pressure, the weight flow of the fluid film and secondary steam, the Reynolds criterion, the velocity of the fluid film and secondary steam, pressure drop along the heating tube [8]. Figure 1 shows the co-directional motion of the solution film and the secondary vapor.…”

Section: Methodsmentioning

confidence: 99%

Investigation of the inlet useful temperature difference effect on the distribution of hydrodynamic characteristics of the vapor-liquid flow inside the falling-film evaporator heating tube designed for a nitric acid solutions evaporation

Khomyakov,

Gushshamova,

Mordanov

et al. 2024

J. Phys.: Conf. Ser.

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We present the results of mathematical modeling of effect of inlet useful temperature difference on the vapor- liquid flow in the heat exchange tube of a vertical evaporating film apparatus, which is designed for evaporation of nitric acid solutions. Distributions obtained along the heat exchange tube length of local values of the: mass flow rate of the fluid and secondary steam, the velocity of the fluid film, the velocity of the secondary steam, the Reynolds criterion of the liquid and vapor phases, the absolute pressure depending on the values of this useful temperature difference. The study was carried out using numerical simulation. To study the effect of the initial useful temperature difference on the hydrodynamics of the vapor-liquid flow, the vertical evaporator equipped with the tube ø38x3 mm and length of L = 4 m was adopted. The linear nature of the distribution of hydrodynamic parameters along the length of the heat exchange tube is established. The absolute pressure in the tube space decreases along the heating tube due to pressure drop. The limiting factor in reducing the absolute pressure is the friction losses of the secondary vapor on the solution film surface. A decrease in the pressure in the tube space leads to decrease in the boiling point of the solution. This leads to increase useful temperature. This has a positive effect on the evaporation efficiency The obtained data should be used in the design of evaporation plants, which are designed for evaporation of nitric acid solutions.

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Section: Methodsmentioning

confidence: 99%

Investigation of the inlet useful temperature difference effect on the distribution of hydrodynamic characteristics of the vapor-liquid flow inside the falling-film evaporator heating tube designed for a nitric acid solutions evaporation

Khomyakov,

Gushshamova,

Mordanov

et al. 2024

J. Phys.: Conf. Ser.

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“…The measurement points are located at r = 43 and 109 mm from the disk centre. For detailed information on the measurement method and data processing of the confocal chromatic sensors in film flows, see Hu et al (2021) and Ubara, Sugimoto & Asano (2022). The time series of interface displacement include the mechanical vibration of the motor-disk system, which has a much slower time scale than the dynamics of surface waves.…”

Section: Experimental Set-upmentioning

confidence: 99%

Low-order modelling of three-dimensional surface waves in liquid film flow on a rotating disk

Kim,

Kim

2024

J. Fluid Mech.

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Using low-dimensional numerical simulations, we investigate the characteristics of complex and three-dimensional surface waves in a liquid film flowing over a rotating disk, focusing on large flow rates from a nozzle. Existing integral boundary layer (IBL) models, which are based on spatially averaged variables along the direction normal to the disk surface, have primarily focused on the formation of axisymmetric waves under relatively small flow rates. In this study, an extended IBL model that accounts for both laminar and turbulent regimes is developed by considering the non-uniformity of the local flow rate in the spreading film flow and incorporating closure models dependent on the local Reynolds number. Our numerical results successfully capture the generation of concentric waves by an impinging circular liquid jet and their transition into three-dimensional solitary waves. These findings are in good agreement with visualization images and time-series data of free-surface fluctuations from a displacement sensor. The backscattering of small-scale three-dimensional turbulence into large-scale horizontal turbulence inside the film plays a critical role in determining the transition of wave modes and the nonlinear dynamics of the waves in the turbulent regime. Furthermore, the behaviour of three-dimensional waves in the downstream region, including frequent wave coalescence in the transition region and the breakup of small-scale solitons, is distinct from that of gravity-driven falling film flows. The amplitude of the three-dimensional waves is inversely related to the generalized Reynolds number defined for rotating films.

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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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Hydrodynamics numerical simulation of a vertical falling film evaporator for ionic liquid systems

Cited by 11 publications

References 49 publications

Investigation of the inlet useful temperature difference effect on the distribution of hydrodynamic characteristics of the vapor-liquid flow inside the falling-film evaporator heating tube designed for a nitric acid solutions evaporation

Investigation of the inlet useful temperature difference effect on the distribution of hydrodynamic characteristics of the vapor-liquid flow inside the falling-film evaporator heating tube designed for a nitric acid solutions evaporation

Low-order modelling of three-dimensional surface waves in liquid film flow on a rotating disk

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

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