A comprehensive simulation and optimization on heat transfer characteristics of subcooled seawater falling film around elliptical tubes

Wan, Zhihua; Li, Yanzhong; Wang, Xin Wei

doi:10.1016/j.applthermaleng.2021.116675

Cited by 21 publications

(8 citation statements)

References 48 publications

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“…It increases by 30.6%, 47.4%, and 44.4% for ϕ = 30°, 60°, and 90° cases from St = 0.14 to St = 0.24. The sudden increase of h avg may be caused by the enhancement of vortices, which was also observed in previous works 36–38,52,53 . The following unchanged h avg at St ≥ 0.24 occurs by two balance effects: on one hand, the higher St can produce larger vortices, which contributes to the heat transfer; but on the other hand, the higher St can reduce the film velocity because of the greater barrier.…”

Section: Resultssupporting

confidence: 76%

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Numerical study of the falling film wettability and heat transfer on the inclined plates with different corrugated structures

Wan

2021

Asia-Pacific J Chem Eng

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In this study, 2D and 3D models of corrugated plates using the volume of fluid (VOF) model were set up to simulate the influence of corrugated structure on the wettability and heat transfer. The results show that compared with the triangular corrugation, the rectangular corrugation has a slower growth rate of wetting ratio (WR) as the Weber number (We) increases under the same corrugation length Le and corrugation depth De. The average WR of the triangular corrugation is 2.8% less than that of the smooth plate. For the triangular corrugation, the higher Le contributes to improving wettability, but the average heat transfer coefficient havg first decreases to the minimum at Le = 5 mm and then increases 8% to 9% to a steady value until Le = 8 mm. WR decreases with De at We ≤ 0.76. A WR correlation considering the corrugation steepness St (St = De/Le) and a critical Re correlation corresponding to the minimum wetting rate were fitted for the liquid oxygen. As the inclination angle ϕ increases, the average film thickness decreases and havg increases until ϕ = 75°, while the variation rate slows down afterwards. At Re = 1200, havg has a decreasing trend at St ≤ 0.13, increases at St ≥ 0.14 and reaches a plateau after St = 0.24 as St increases. It increases by 30.6%, 47.4%, and 44.4% for the inclination angle ϕ = 30°, 60°, 90° cases from St = 0.14 to 0.24. The enhancement is caused by the vortices existing at St ≥ 0.14.

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Section: Resultssupporting

confidence: 76%

“…It also shows the h results of the triangular corrugation and the smooth plate both reduce along the flow direction. The reason behind this can be elucidated from the development of the thermal boundary layer 52,53 . To have a better view of h and δ , the local scope figure for the range of y = 24–36 mm is enlarged in Figure 11b.…”

Section: Resultsmentioning

confidence: 99%

Numerical study of the falling film wettability and heat transfer on the inclined plates with different corrugated structures

Wan

2021

Asia-Pacific J Chem Eng

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“…The problem of two-phase interface is usually calculated by capturing the phase interface and performing numerical simulation. The more commonly used methods are the Volume of Fluid (VOF) method [19][20][21] and the Level Set (LS) method [22,23]. In this article, the VOF method is used to track the gas-liquid interface to study the motion of bubbles.…”

Section: Governing Equationmentioning

confidence: 99%

Numerical Study on the Rising Motion of Bubbles near the Wall

Zhang

Chen

et al. 2021

Applied Sciences

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Based on the volume of fluid method (VOF), the rising characteristics of bubbles in near-wall static water are studied. In this study, the influence of the wall on the rising motion of the bubble was studied by changing the distance of the bubble wall, the diameter of the bubble, the arrangement of the bubble and the size ratio, etc. The influence is expressed as the average swing amplitude of the “Z”-shaped motion when the bubble rises. The study found that in the case of a single bubble, the wall surface has a certain influence on the rise of the bubble, and its degree is affected by the bubble wall distance and the bubble diameter. The influence of bubble wall distance is more obvious. The greater the bubble wall distance, the less the bubble is affected by the wall; in the case of double bubbles, the influence of the interaction force between the bubbles is significantly greater than the wall surface.

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“…Falling film technology has the advantages of low pressure drop, high heat and mass transfer, small liquid charge, which has been widely used in many fields such as desalination, refrigeration, chemical processes. The structures for the falling film evaporators include plates, tubes, packed columns and so on [1][2][3][4]. The falling film evaporators contribute to energy saving, while there are many factors influence on the heat and mass transfer performance.…”

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 comprehensive simulation and optimization on heat transfer characteristics of subcooled seawater falling film around elliptical tubes

Cited by 21 publications

References 48 publications

Numerical study of the falling film wettability and heat transfer on the inclined plates with different corrugated structures

Numerical study of the falling film wettability and heat transfer on the inclined plates with different corrugated structures

Numerical Study on the Rising Motion of Bubbles near the Wall

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

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