Experimental study on fluid flow and heat transfer characteristics of falling film over tube bundle

Yan, Wei‐Mon; Pan, Chun-Wei; Yang, Tsung Hsun; Ghalambaz, Mohammad

doi:10.1016/j.ijheatmasstransfer.2018.10.070

Cited by 45 publications

(10 citation statements)

References 24 publications

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“…The flow parameters such as jet shape and diameter are observed for different distributor heights and orifice spacing. Yan et al 18 conducted experiments to investigate the liquid film behavior and variation in FT for various Re and nozzle spacing distances.…”

Section: Introductionmentioning

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 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%

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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“…Despite the numerous benefits listed above, gravity-powered FFEs have major downsides such as improper liquid film distribution, the formation of dry spots and flooding, and waste of fluid and energy [11]. All of the factors mentioned above are strongly linked to the heat transfer mechanism [12]. Dry spots on the tube walls and uneven liquid film coverage have all led to a substantial deterioration in the evaporation process.…”

Section: Introductionmentioning

confidence: 99%

A 2-D numerical study of contact angle effect on transient falling-film flow over horizontal tubes

Kandukuri¹,

Deshmukh²,

Katiresan³

2022

Preprint

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The coverage of the liquid film over the horizontal tubes, particularly the wetting ratio, is important for heat transfer mechanism of gravity-driven evaporators and absorbers. A 2D, two-phase CFD model was developed to examine the falling-film hydrodynamics and transient flow mechanism for Reynolds numbers ranging from 100-500, contact angles spanning from 0°/30°/60°/90°, and inter tube spacing of 10 mm. The VOF method is used in this article to capture the gas-liquid interface. The findings showed that the complete spreading of the liquid film is difficult at low Reynolds numbers and high contact angles. The formation of dry regions on the tube wall as a result of insufficient liquid supply, liquid film breakage, and liquid film shrinkage. Furthermore, as the Reynolds number increases and contact angle decrease, the wetting ratio over the tube surface increases. It was worth noting that each contact angle must have a minimum Reynolds number in order to keep the surface completely wet. The research also found that for higher Reynolds numbers, the influence of contact angle on wettability of tube wall can be ignored. The liquid propagation time required to wet the tube surface increases as the contact angle value increases for the same Reynolds number. Fouling over the tubes can be aided by the formation of air voids near the lower stagnation zone.

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“…By modeling the effects of rectangular and circular atomization holes on the drop film evaporation process, Lin et al [12] discovered that under the same Re conditions, there was little variation in the impact of rectangular and circular holes on the film thickness. Yan et al [13] found that the position of the nozzle hole has a considerable impact on the test tube's heat transfer and fluid flow characteristics. Qi et al [14] conducted experimental studies and numerical simulations on the heat transfer and flow of the external drop film of an elliptical tube and found that the h θ of the elliptical tube was 20 to 22% larger than that of the circular tube.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer Study from a Salty Droplet Film on a Horizontal Tube in Mechanical Vapor Recompression Crystallization System

et al. 2022

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The horizontal drop film evaporator is a key component of the mechanical vapor recompression crystallization system, which can be used to evaporate effluent and recycle secondary vapor energy. However, the properties of heat transfer and flow of the salty effluent sprayed external of the horizontal drop film evaporation tube are obviously different from that of ordinary water. We established a 3D model for a horizontal drop film evaporator in the system, and water and sodium sulfate mixture were manufactured to reproduce the real salty effluent. By applying the VOF (volume of fluid) model, the liquid-gas interface of a salty effluent spray drop film formed on a horizontal tube in the evaporator was traced. The impacts of various heat flux, sodium sulfate content, spray density, and temperature on the local Nusselt number were studied, and a dimensionless correlation was established. The results showed that the effect of surface tension cannot be negligible; as the sodium sulfate content rises, the local Nusselt number declines in the thermal developing region; as the spray temperature and density rises, the local Nusselt number rises, which was largely independent of the heat flux in the thermal developing region.

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Experimental study on fluid flow and heat transfer characteristics of falling film over tube bundle

Cited by 45 publications

References 24 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

A 2-D numerical study of contact angle effect on transient falling-film flow over horizontal tubes

Heat Transfer Study from a Salty Droplet Film on a Horizontal Tube in Mechanical Vapor Recompression Crystallization System

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