Numerical and experimental investigation on the heat and mass transfer of falling film and droplet regimes in horizontal tubes LiBr-H2O absorber

Zhang, Huan; Yin, Dazhen; You, Seung-Kyong; Zheng, Wandong; Li, Bojia; Zhang, Xinyu

doi:10.1016/j.applthermaleng.2018.10.046

Cited by 23 publications

(5 citation statements)

References 17 publications

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“…The region of interest (ROI) method was used to observe the specifications of falling droplets. The study of Zhang et al 26 divulged the development of droplet flow regimes of LiBr‐H 2 O on horizontal tubes. The growth of area and volume of a droplet for different Re is noticed.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of column flow regimes on horizontal tubes for falling‐film systems: An experimental approach

Kandukuri

Deshmukh

Katiresan

2022

Asia-Pacific J Chem Eng

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The intertube flow regimes and hydrodynamic behavior of the liquid profile have a significant impact on the functioning of falling-film evaporators. Column flow is one of the fundamental flow modes, which is actively observed in many industrial evaporators. A high-speed digital photographic device is utilized to visualize the complete progression of column flow phases for intertube distances of 10/20/30/40 mm and Reynolds number (Re) values ranging from 41 to 583. The Sobel edge detection algorithm is implemented to quantify the flow parameters for each frame of a sequence. The research results indicated that the column flow regime between the inline horizontal tubes can be broadly classified into the following phases: columnar droplet flow, periodic column flow, satellite drops column flow, drift column flow, and mixing liquid film column flow. The findings show that the liquid jet diameters between the tubes range from 1.6 to 8.46 mm, an increase in the liquid jet diameter with Re and a decrease with tube-to-tube distance. The axial coverage of the liquid film profile beneath the tube differed from 2.07 to 3.99 mm and over the tube surface ranged from 1.14 to 2.68 mm. The formation of dry spots and flooding is a major problem in the operation of falling-film heat exchangers. The shape and size of the liquid jet have a direct impact on the interfacial area; understanding the entire progression of column flow regimes, as well as their characteristics, can help designers avoid the aforementioned problem.

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Section: Introductionmentioning

confidence: 99%

“…The region of interest (ROI) method was used to observe the specifications of falling droplets. The study of Zhang et al 26 Nusselt first suggested falling-film theory, assuming a complete sheet mode from one tube to another subsequent tube. The following expression is to assess the FT for various peripheral angles 29 :…”

mentioning

confidence: 99%

Characterization of column flow regimes on horizontal tubes for falling‐film systems: An experimental approach

Kandukuri

Deshmukh

Katiresan

2022

Asia-Pacific J Chem Eng

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“…The increase in the surface contact angle elevated the resistance to the axial motion of the film, which inhibited the spreading of the film and decreased the mass transfer. Zhang et al 18 studied the flow pattern transformation of a ripple tube. It observed that the ripples promote the lateral motion of the film and reduce the interval between the liquid jets.…”

Section: Introductionmentioning

confidence: 99%

“…The maximum volume and area of the droplet’s aerial motion were 200 mm 3 and 180 mm 2 , respectively . The motion of the film front around the round and rectangular tubes was analyzed using a high-speed camera, and the result showed that the circumferential velocity of the film front of the droplet could reach 0.4–0.6 m/s. , Zhang et al analyzed the evolution of the volume during the motion of the droplet and its mass transfer property and demonstrated that the droplet formation process would wash out and disturb the surrounding flow field. In addition, the formation stage of the pendant droplet contributed >50% of the mass transfer.…”

Section: Introductionmentioning

confidence: 99%

Motion Evolution Mechanism of Falling Film over Horizontal Tube at Low-Spray Density

Zheng

Zhao

Wang

et al. 2022

Ind. Eng. Chem. Res.

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Horizontal falling film absorber has been widely applied in petroleum, chemical industry, and toxic gas disposal due to its advantages of large fluctuation of gas–liquid interface, accurately controlled interface, easy separation of gas–liquid interface, and low-pressure drop. The study of the velocity evolution of the liquid film at low-spray density is essential to understand the micro-mass transfer mechanism of the reactor and strengthen the absorption. The present study first deciphered the subregion features of the falling film motion over a horizontal tube with varied flow patterns and the parameters, such as spray density, spray height, and salinity that affects the velocity distribution of the falling film at low-spray density for the superhydrophilic surface, were also investigated using the modified PIV method. The result indicated that the velocity distribution of the film renders a typical subregion effect, i.e., nonimpact zone and impact zone for droplet mode, while, for jet mode, the film between the adjacent columns exists in the form of mutual repetition, and the velocity of the film will be slightly higher than that of the body motion region at the interaction ring. It was also found that the spray density and spray height had a positive effect on the average velocity of falling film over the horizontal tube for droplet mode and jet mode. However, for the droplet mode, the spray density increases the velocity of the film by increasing the frequency of the droplet impact. In addition, the average velocity of the film decreases with the increase in the salinity (viscosity).

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“…Falling film flow outside a horizontal tube or between horizontal tubes has been studied by a lot of researchers − because this form is widely used in evaporation heat transfer. The flow patterns depend largely on the structure parameters (pipe diameter, pipe spacing) and operating conditions (spray density and fluid properties) and can be summarized as the drop-like flow, drop-like column flow, column-like laminar flow, and plate-like flow.…”

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 and experimental investigation on the heat and mass transfer of falling film and droplet regimes in horizontal tubes LiBr-H2O absorber

Cited by 23 publications

References 17 publications

Characterization of column flow regimes on horizontal tubes for falling‐film systems: An experimental approach

Characterization of column flow regimes on horizontal tubes for falling‐film systems: An experimental approach

Motion Evolution Mechanism of Falling Film over Horizontal Tube at Low-Spray Density

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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