CFD simulation of water vapor absorption in laminar falling film solution of water-LiBr ─ Drop and jet modes

Hosseinnia, Seyed Mojtaba; Naghashzadegan, Mohammad; Kouhikamali, R.

doi:10.1016/j.applthermaleng.2017.01.022

Cited by 48 publications

(11 citation statements)

References 31 publications

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“…Their analysis showed that the mass transfer mechanism is greatly affected by the flow mode, as the absorption rate was decreased more than 10-fold when the flow mode was changed from droplet to jet. For this reason, most of the absorber operates under droplet, droplet-jet, and modes or low liquid load [9,20]. The film distribution around the tube can be divided into stagnation, impingement, developing, developed, detachment, and necking regions.…”

Section: Problem Statementmentioning

confidence: 99%

“…In 1916, Nusselt established the film thickness δ correlation as a function of angular position θ, liquid load Γ 1/2 , and thermophysical properties [18]. The Nusselt solution, as shown in Equation 7, is widely used for thickness estimation and comparison purposes [9,[19][20][21]:…”

Section: Introductionmentioning

confidence: 99%

“…Based on their CFD results, they proposed a film thickness correlation similar to Hou et al [24], but with different parameters for three sections, namely impingement, transition, and departure regions. Hosseinnia et al [20] carried out a numerical analysis for mass transfer mechanism in the LiBr-based absorber. The VOF model and h-refinement (a mesh adaptation technique) were implemented in order to solve conservation of mass, momentum, and energy equations.…”

Section: Introductionmentioning

confidence: 99%

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CFD Analysis of Falling Film Hydrodynamics for a Lithium Bromide (LiBr) Solution over a Horizontal Tube

2020

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Falling film evaporators are used in applications where high heat transfer coefficients are required for low liquid load and temperature difference. One such application is the lithium bromide (LiBr)-based absorber and generator. The concentration of the aqueous LiBr solution changes within the absorber and generator because of evaporation and vapor absorption. This causes the thermophysical properties to differ and affects the film distribution, heat, and mass transfer mechanisms. For thermal performance improvement of LiBr-based falling film evaporators, in-depth analysis at the micro level is required for film distribution and hydrodynamics. In this work, a 2D numerical model was constructed using the commercial CFD software Ansys Fluent v18.0. The influence of the liquid load corresponding to droplet and jet mode, and the concentration, on film hydrodynamics was examined. It was found that the jet mode was more stable at a higher concentration of 0.65 with ±0.5% variation compared to lower concentrations. The recirculation was stronger at a low concentration of 0.45 and existed until the angular position (θ) = 10°, whereas at 0.65 concentration it diminished after θ = 5°. The improved heat transfer is expected at lower concentrations due to lower film thickness and thermal resistance, more recirculation, and a higher velocity field.

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Section: Problem Statementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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CFD Analysis of Falling Film Hydrodynamics for a Lithium Bromide (LiBr) Solution over a Horizontal Tube

2020

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“…The present analysis focuses on an absorptive liquid film flowing over a vertical row of horizontal smooth tubes. Droplet impact and hydrodynamic boundary layer development (19)(20)(21)(22)(23)(24)(25)30) are not discussed herein. In order to reach a closed analytical solution of the governing transport equations, heat and mass transfer processes are considered under the following main assumptions:…”

Section: Physical Modelmentioning

confidence: 99%

Heat and mass transfer coefficients of falling-film absorption on a partially wetted horizontal tube

Giannetti

Rocchetti

Yamaguchi

et al. 2018

International Journal of Thermal Sciences

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“…Various experiments and investigations were carried out to investigate the influences of the liquid properties, tube diameter, flow rate, and tube spacing on the flow state and falling-film thickness on the horizontal smooth tubes. ,− However, due to the limitation of sensor resolution and accuracy, some details of the microscopic flow characteristics during the falling-film process, such as the velocity distributions, local film distribution, and so on, may not be fully revealed through experimental studies . As an effective auxiliary means, computational fluid dynamics (CFD) can intuitively provide the complex flow behavior that is difficult to be presented in experimental research. , For example, some researchers have established CFD models based on the volume of fluid (VOF) method to study the transient thin film flow on solid substrates and identified different wetting patterns that may appear. − Furthermore, many researchers ,− conducted CFD studies on the flow characteristics of horizontal smooth tubes during falling-film evaporation. For example, Lin used a three-dimensional coordinate axis to explore the film thickness distribution of the smooth tube.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Flow Behavior of a Falling Film on Horizontal Tubes: A Comparative Study on Smooth and Finned Tubes

Cao

Xie

et al. 2022

Ind. Eng. Chem. Res.

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In this work, the two-phase flow behavior of a falling film on horizontal smooth and finned tube systems was investigated and compared using a three-dimensional computational fluid dynamics model based on the volume of fluid method. The model was established to capture the microscopic gas–liquid interface of the falling film for smooth and finned tubes. The three-dimensional flow behavior of the falling film, including the liquid film spreading, the film thickness, the velocity distribution, and the effect of Reynolds number (Re) on the film distribution, was investigated systematically. The results show that the liquid film spreads on the smooth tube rapidly and forms a film thickness distribution of “crest-stable-crest”, while the axial spreading of the liquid film is significantly restricted and hindered by the fins on the finned tubes. The falling films of the smooth tube and the finned tube present a staggered column flow and an in-line column flow, respectively. Besides, the axial liquid film spreading on the smooth tube is more sensitive to the Re compared with the finned tubes. The finned tube with a lower fin density achieves better axial spreading, and the finned tube is completely covered by the liquid film at Re = 521 with an optimized liquid column spacing.

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CFD simulation of water vapor absorption in laminar falling film solution of water-LiBr ─ Drop and jet modes

Cited by 48 publications

References 31 publications

CFD Analysis of Falling Film Hydrodynamics for a Lithium Bromide (LiBr) Solution over a Horizontal Tube

CFD Analysis of Falling Film Hydrodynamics for a Lithium Bromide (LiBr) Solution over a Horizontal Tube

Heat and mass transfer coefficients of falling-film absorption on a partially wetted horizontal tube

Three-Dimensional Flow Behavior of a Falling Film on Horizontal Tubes: A Comparative Study on Smooth and Finned Tubes

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